LONDON - British Prime Minister Rishi Sunak unveils his Conservatives' agenda for government on Tuesday, promising to offer voters in an election on July 4 the kind of financial security he says the opposition Labour Party can never provide.

With his governing party well behind in the opinion polls just weeks before the national election, Sunak will again try to convince voters that he has a bold plan to cut taxes, boost the economy and curb migration.

He (Rishi Sunak) will again attack Labour leader Keir Starmer and his team, repeating an accusation that the party will increase taxes by more than 2,000 pounds ($2,545) on working households - a charge Labour says is a lie and which has been questioned by economists

So far, his message has failed to start closing the gap with Labour, and he now faces a challenge from the right-wing Reform UK party, which, under the leadership of Brexit campaigner Nigel Farage, has vowed to lead a "revolt" against the Conservatives.

READ MORE: In heated debate, Britain's Sunak, Starmer go head-to-head on the economy

The launch of the party's manifesto, a document which sets out which policies the party will pursue if in government, is yet another roll of the dice for Sunak, who is expected to make much of his already-announced tax cuts and who could go further.

"We Conservatives have a plan to give you financial security," he will say at the manifesto launch, according to excerpts of his speech.

"We will enable working people to keep more of the money you earn because you have earned it and have the right to choose what to spend it on."

He will again attack Labour leader Keir Starmer and his team, repeating an accusation that the party will increase taxes by more than 2,000 pounds ($2,545) on working households - a charge Labour says is a lie and which has been questioned by economists.

READ MORE: UK says Rwanda asylum seekers' deportation flights to begin on July 23

In what has become a rancorous campaign, Sunak will champion Conservative pledges to protect pensions, a guarantee not to raise income tax, national insurance or VAT, and what he describes as a tax cut for parents.

He will also repeat his pledge to abolish "the double tax on work when financially responsible to do so" - a reference to scrapping the national insurance payroll tax.

READ MORE: UK parliament dissolves ahead of July general election

But he is on the back foot. An early departure from D-Day commemorations in France alongside other world leaders last week backfired when veterans were angered, prompting members of his party to question his decision-making skills. Sunak apologised.

Before the manifesto launch, Labour said the document would be "littered with unfunded commitment after unfunded commitment". "Whatever the Tories announce tomorrow, the money is not there," said Labour's Jonathan Ashworth.