Top lawmakers lashed out Monday at Gov. Mitt Romney's veto of a pre-kindergarten education bill, as Lt. Gov. Kerry Healey's gubernatorial campaign defended what a top Romney adviser conceded was a politically difficult position.

The co-chairs of the Legislature's Committee on Education said they hoped the House and Senate return later this year in formal sessions to try to override the veto of a Department of Early Education and Care (DEEC) bill, although both conceded they were unaware of any such plans.

"I don't think he really understands what this legislation was meant to do. It's the next step in refining that department," said House Education Committee chair Patricia Haddad (D-Somerset), who called the bill a guidebook for a state effort to furnish universal access to pre-kindergarten education.

Romney vetoed the bill Friday, after lawmakers had rejected his plan to change the bill by cutting out the language to expand state commitments for pre-K education. Rather than commit immediately to what he said could be a $1 billion-plus per year hit to taxpayers, Romney encouraged waiting for the results, due next February, of a $4.6 million pilot program provided for in this year's budget.

The department, which falls under Romney's oversight, had worked with legislators in authoring the bill (H 4755), the follow-up to the department's 2004 enabling statute. But Romney dismissed the expansion as "an expensive entitlement," and said it laid the groundwork for future tax increases.

"We were supportive of the legislation," said department spokeswoman Amy Kershaw. "It has a lot of important implications for us, and we also understand the governor's concern."

Asked the veto's impact on the department, Kershaw replied, "The bill definitely would have provided further clarification for the purpose and the structure of our agency . . . but the language in the existing statute is sufficient for us to continue our current work while the legislation is still being refined."

She declined to answer a question about if DEEC officials were disappointed in the veto.

On Monday, the House added the governor's veto to its calendar. Despite the plan's unanimous passage in the House and Senate, it's unlikely that a veto could be overridden during informal sessions because roll calls are not taken during informals, when an objection from a single lawmaker in either branch dooms a motion. There are no public plans for special formal sessions before next year.

"This would have provided some real direction and definition to this new department," said Sen. Robert Antonioni, the committee's Senate chair. He said the Legislature should return in the fall for override opportunities.

Romney communications director Eric Fehrnstrom said, "The Legislature's appetite for new spending knows no bounds, but the governor feels an obligation to the taxpayers to look out for their interests."

Passed unanimously by the House in March but handled more slowly in the Senate, the bill would have infused the two-year-old early education bureaucracy with more specified powers, and at the same time installed measures, through diverse advisors, to check those abilities.

The legislation avoided both pinning a cost on the program and identifying a revenue source - in part, Haddad said, because the bill instructed the department to conceive of a five-year plan, with subsequent details to be worked out based on that blueprint.

"We can't talk about a revenue source until we know what the actual cost is going to be," Haddad said.

In Arkansas, Haddad noted, the state relies on a 3 percent "beer tax" (about 18 cents per six-pack) to pay for its early education expansion, and advocates here have weighed similar funding mechanisms.

In a telephone interview, Fehrnstrom said, "The politically easy choice for Gov. Romney would have been to approve this massive new spending program as he's ending his term in office and let someone else figure out how to pay for it. Instead, the governor is being honest with the people of Massachusetts, and the folks who are in favor of universal pre-K should be required to identify a funding source."

A spokesman for House Speaker Salvatore DiMasi said in an emailed statement that Romney's veto meant Romney had "flipped his position" since 2004, when he signed the law creating the department.

Two Democratic gubernatorial candidates last week quickly ascribed a portion of the blame to Republican candidate Kerry Healey, Romney's lieutenant governor.

In press releases, Attorney General Thomas Reilly labeled the veto "incredibly shortsighted," and Christopher Gabrieli, whose education think tank has advocated for longer school days, called it "unfortunate that Kerry Healey claims she supports early education one minute, while it is vetoed the next."

In statements Monday, both Democrat Deval Patrick and independent Christy Mihos faulted the decision.

Patrick faulted Romney for "a big mistake," and Mihos ripped as "disgraceful" the administration's decision: "If Kerry Healey cannot convince Romney to support early education as she claims she does, how meaningful is anything she has promised?"

Haddad, who is supporting Gabrieli, also criticized Healey: "Where was the lieutenant governor on this? She didn't go to bat for us on this, obviously."

Healey campaign spokeswoman Amy Lambiaso responded to Reilly's and Gabrieli's criticisms: "This is another billion-dollar proposal by Gabrieli and Reilly that they have no way to pay for besides raising taxes."

Healey supports the veto, Lambiaso said, "for the reasons that [Romney] outlined in his veto message."

With lopsided partisan majorities in both branches, the Legislature could have rendered a Romney veto irrelevant - as it often does - by passing the bill earlier and giving themselves time to override his veto.

But the Education Committee chairs were loath to let blame for the bill's failure rest with lawmakers.

"You can't play the what-if game," Haddad said. "I don't think that people actually thought he would veto it. I'm shocked, based on how much work we put into it. If people sit down and look at it, they see it for what it is: the next step in the process. Everywhere you look in this bill, it talks about 'subject to appropriation.' I think I know the people in this building well enough to know that they are not going to appropriate money for something that is not firm and solid."

Said Antonioni, "I would be hard-pressed to blame the Legislature here for this…[Romney] had plenty of time to check with us about what his concerns were, and he didn't do that. It is what it is."

Antonioni added, "I think at the end of the session there is a bottleneck sometimes, and it just got held up. I don't think it was anything purposeful."