The Progressive Conservatives under Alward are pushing a plan to develop a shale gas industry as a way to create jobs and spur economic growth.
Gallant used the Tories campaign slogan of "Say Yes!" in taking aim at the government's record since it was first elected four years ago.
"Does that mean that they have to say 'Yes' to continued job losses that they've seen under your government?" he asked. "Does that mean than they have to say 'Yes' to Stephen Harper's EI changes? Does that mean that they have to say 'Yes' to the worst economic growth year after year under your government?"
Alward fired back, saying the Liberal platform, which includes $900 million in infrastructure spending, is no plan at all.
"In 2010, when your previous premier was spending the most money in capital budget history in New Brunswick, you lost 7,000 jobs," Alward said. "Your plan for the future is false. ... All it will do is put money from people's wallets into long-term debt of the province."
Gallant reminded voters that the Tories have failed to balance the budget in four years as promised. But Alward said that's because it is taking the Tories longer to correct the financial problems left by the previous Liberal government of then-premier Shawn Graham.
The English-language debate was recorded for broadcast Friday on Rogers Cable stations in New Brunswick. Another debate was held Wednesday in French.
For the first time in the debates that have been held so far in the campaign for the Sept. 22 election, the leaders were asked about abortion, which has become an issue since the recent closing of the Morgentaler Clinic in Fredericton.
It was the only private facility to offer abortions in the province and its closing triggered protests over New Brunswick's rules governing access to the procedure.
By law, a woman who wants an abortion covered by medicare must have two doctors certify in writing that it is medically necessary and the procedure must be carried out by a specialist in one of two approved hospitals.
Gallant said if he wins the election, the Liberals will launch a study to find all the barriers to abortion and remove them.
But that answer drew criticism from NDP Leader Dominic Cardy, who tried to pin down Gallant on whether he would specifically cancel the section of the Medical Services Payment Act that requires a woman to receive the approval of two doctors.
"Yes or no Mr. Gallant?" Cardy asked without getting a specific answer.
Cardy and Green party Leader David Coon said they would repeal the regulation, while Alward and Kris Austin of the People's Alliance of New Brunswick said the province provides adequate access to medically necessary abortions.
Coon also touted his plan for greener forms of energy and a tax on pollution.
Earlier Wednesday, Coon announced he would implement a tax on soft drinks and direct that revenue to fund food and wellness programs in schools.
Cardy said he would introduce a plan to help graduates pay off their student loans within eight years by bringing in post-graduation bursaries and eliminating the interest on student loans.