Older voters overwhelmingly want the Conservative Party to ditch long-term plans to abolish National Insurance over fears it will hit pensions.

The influential campaign group Silver Voices says 99% of its members oppose the “ambition” which was announced by Jeremy Hunt during this month’s Budget.

They say the move threatens the £124 billion-a-year state pension which is paid for by the £172 billion annual NI pot.

Silver Voices director Dennis Reed warned the strategic “miscalculation” could cost the Tories votes at the general election.

He said more than 1600 over-60s were surveyed last week, with almost everyone opposed to abolishing NI.

In his Budget the Chancellor announced a 2p cut to NI in addition to the 2p cut unveiled in last year’s Autumn Statement.

He also signalled it was the Tory Party’s aim to scrap National Insurance in the long run, labelling it as a “double taxation” on workers when combined with income tax.

Mr Hunt has since denied that pensions would be hit and insisted his Budget has done an “enormous amount” for pensioners.

But Mr Reed believes that scrapping NI would unpick the whole basis of the Welfare State and place the continuation of the universal state pension in great peril.

He said: “The Conservatives may have made a major miscalculation in proposing the long-term abolition of National Insurance.

“They would be unpicking the basis of the agreement reached with the British People after the Second World War in setting up the Welfare State, and threatening the continuation of a universal state pension. If our poll is anything to go by, this will be a wildly unpopular proposal which is likely to lose them millions of older voters, despite their welcome commitment to the Triple Lock.

“I do not think that the implications of this last-minute addition to the Budget Speech have been fully thought through and urge the Government to wipe the slate clean and think again”.

It comes as new research from the Resolution Foundation shows that a basic-rate pensioner may see their above-inflation State Pension rise (£190) virtually wiped out by this April’s personal allowance freeze (£170).

The Treasury has been asked for a comment.