VOTERS are not being offered an "honest set of choices" on tax and spending by the two main political parties amid concern over gaps and mistakes in their manifestos, the Institute for Fiscal Studies, has claimed.

The respected economic think-tank flagged up factual errors in Labour's calculations, warning its tax hikes aimed at top earners and businesses might "not raise anything like" the £48.6 billion claimed and that the party's proposals could turn out to be "economically damaging".

Meantime, it warned that under the Conservatives’ plans Britain could face "another parliament of austerity,” saying continued belt-tightening might cause serious damage to the ability to deliver public services and it set out serious doubts over the deliverability of the Tory plans for the NHS in England.

The IFS also condemned Conservative moves to curb net migration to 100,000, saying it risked a £6 billion hit to the Exchequer.

Giving his assessment of the parties' plans, Carl Emmerson, its deputy director, said: "The shame of the two big parties' manifestos is that neither sets out an honest set of choices.

"Neither addresses the long-term challenges we face. For Labour, we can have pretty much everything: free higher education; free childcare; more spending on pay; health; infrastructure. And the pretence is that can all be funded by faceless corporations and 'the rich'.

"There is a choice we can make as a country to have a bigger state. That would not make us unusual in international terms.

"But that comes at a cost in higher taxes which would inevitably need to be borne by large numbers of us," he explained.

Labour, said the IFS, would "raise spending to its highest level since the mid-1980s and tax to record levels in peacetime" and it queried whether taxes such as the offshore tax levy and the cap on excess pay would generate income.

The think-tank also pointed to Labour’s "risky" plans to boost corporation tax amid uncertainty over Brexit, while claiming that plans to boost minimum wage could be "economically damaging".

"Clearly, one risk with Brexit is investment falls within the UK economy and clearly it may mean that it's not the time to put up corporation tax significantly,” said Mr Emmerson. "It may be that is a particularly risky thing to do at that moment in time," he added.

Turning to the Tory manifesto, the IFS chief dismissed Theresa May's proposals to means-test winter fuel payments for the elderly and scrap the pensions triple lock as making "wholly trivial" savings.

He said the party’s manifesto U-turn over a cap on care costs would result in "presumably increasing public spending overall".

Mr Emmerson said: "The Conservatives simply offer the cuts already promised. Additional funding pledges for the NHS and schools are just confirming that spending would rise in a way broadly consistent with the March Budget.

"Compared with Labour, they are offering a relatively smaller state and consequently lower taxes. With that offer come unacknowledged risks to the quality of public services, and tough choices over spending."

He added that the Tory commitment to get net migration down to the "tens of thousands" risked causing "considerable economic damage", particularly when coupled with the ageing British population.

The Office for Budget Responsibility has already downgraded its forecasts for tax receipts by £6bn in 2020-21 - and rising thereafter - due to lower expected net immigration.