In her first television interview of the election campaign, the Prime Minister told the BBC’s Andrew Marr she did not want to make specific proposals on taxes unless she was sure she could deliver them.
She had been asked if she would stick to the Tories’ 2015 promise not to raise income tax, VAT or national insurance.
The so-called “tax lock” pledge has proved troublesome for Chancellor Philip Hammond, who was forced into a U-turn after last month's Budget when a revolt from backbench Tory MPs made him ditch planned national insurance changes for the self-employed.
In a second interview on ITV’s Peston on Sunday, the Prime Minister said: “We won’t be increasing VAT.”
She said: “We have no plans to raise the level of tax. In relation to specific taxes, we won't be increasing VAT."
On Marr, she said she intends to cut taxes “on working families” if the Conservatives win the General Election on June 8.
The PM said: "We have absolutely no plans to increase the level of tax but I'm also very clear that we don't want to make specific proposals on taxes unless I'm absolutely sure that I can deliver on those.
"But it would be my intention as a Conservative government and as a Conservative prime minister to reduce the taxes on working families.
"And if you've got strong and stable leadership that's absolutely what you can do."
Mrs May also indicated she would reform the pensions triple lock, another flagship 2015 pledge, promising state pensions would continue to rise with the exact way that is calculated revealed in the Tories' manifesto.
The triple lock ensures the state pension increases in line with wages, inflation or by 2.5 per cent - whichever is highest.
But there have been mounting calls to scrap it, amid concerns over cost pressures.
"Under a Conservative government the state pension will still go up every year of the next parliament," she said.
Mrs May declined to give both interviewers confirmation of what would be in the Tory manifesto and said they would have to wait to see what’s in it.