Lt. Gov. Anthony G. Brown went on the attack Tuesday with a new Web ad suggesting that Attorney General Douglas F. Gansler, a rival Democrat for governor, is more interested in cutting corporate taxes than expanding pre-kindergarten education.

The ad includes footage of Gansler on the campaign trail, touting his plan to cut the state’s corporate income tax rate from 8.25 percent to 6 percent to match that of Virginia. Viewers also see Gansler saying, “Obviously you can’t extend pre-K to full day for all children. It’s not affordable at all.”

From that point, a chorus of what the Brown campaign says are real people weigh in. Among their comments about Gansler: “He’s favoring corporations more than the children of his state,” and “I would think he’s a Republican.”

Bob Wheelock, a spokesman for Gansler, hit back Tuesday afternoon, branding the ad “a lie” and saying that Brown’s advocacy for expanding pre-K programs “sounds hollow” after seven years as lieutenant governor.

All three major Democratic candidates for governor, including Gansler, have proposed an expansion of pre-K programs in Maryland in coming years, though Gansler’s is less ambitious than those of Brown and Del. Heather R. Mizeur (D-Montgomery). Wheelock said it’s wrong to characterize Gansler as not caring about the issue.

Wheelock also took issue with the “cooked up” price tag that Brown’s campaign has put on Gansler’s corporate tax cut proposal: a loss of $1.6 billion in state revenue over five years.

That number, which is not mentioned in the Web ad, reflects a legislative analysis of a plan that has been introduced in the General Assembly to reduce the corporate tax rate from 8.25 percent to 6 percent, as Gansler has proposed.

But Wheelock said the details of Gansler’s plan have not been made public.

“In the coming days, the attorney general will unveil a targeted rollback of the corporate tax, which will encourage businesses to invest in Maryland, create jobs and pay a better wage,” Wheelock said.

Brown has proposed making pre-kindergarten available to all 4-year-olds, regardless of family income, by 2018. That proposal is estimated by his campaign to cost about $138 million a year.

Gansler has pledged to expand the state’s current pre-kindergarten offerings from half-day to full-day programs and expand eligibility to 300 percent of the poverty level. Such an expansion is estimated by his campaign to cost about $20 million a year.

Mizeur, meanwhile, has proposed phasing in full-day pre-K programs for all 4-year-olds and half-day programs for 3-year-olds from lower-income families. Once fully implemented, the cost of the initiative would be close to $280 million a year, according to estimates from her campaign.

Brown’s ad turns the tables on Gansler, who has produced some Web ads highlighting Brown’s role in Maryland’s botched rollout of its online insurance health exchange.

“As for sounding like a Republican, Anthony Brown has done just about everything possible to undermine the president’s health-care law here in Maryland at the expense of Marylanders who desperately need health insurance,” Wheelock said Tuesday. “You would think he is a paid operative for the Republican party.”

Jenna Johnson contributed to this story.