The former Mayor of Greater Manchester worked in Sir Tony's Cabinet for six years

Sir Tony Blair has issued a last-ditch plea to Andy Burnham amid markets' panic over the would-be Prime Minister's plans in office.

The Labour leadership frontrunner is said to considering a tax hike on capital gains tax (CGT) to bring the levy in line with income tax - but his endeavours could be cut short by the former Prime Minister's think tank.

Mr Burnham worked in Sir Tony's Cabinet from 2001 until 2007, working as a Whip and then later becoming Health Minister.

Now, his former boss has weighed through his think tank, The Tony Blair Institute for Global Change, which said that we cannot "tax our way to prosperity" and branded the proposed tax hikes as "bad politics".

One of the think tank's analysts, Guy Ward-Jackson, said that the UK requires long-term investment and the verve to back "new business technologies and ideas".

"We must be a place where entrepreneurs feel they can take risks, build companies, and be rewarded for it – all the while contributing to jobs and growth," he told The Telegraph.

"Increasing capital gains tax to the level of income tax would undermine those incentives and send entirely the wrong signal."

He added that doing so would send "precisely the wrong message at precisely the wrong time".

Instead, Britain must embrace the new technological age to boost growth and security.

During the General Election, Labour's top brass repeatedly vowed not to raise VAT, income tax and National Insurance.

Mr Burnham, last week, vowed to stay true to the manifesto commitments but has fuelled on fevered fiscal speculation as he said there was "some room" for change.

CGT is a tax on the profits made from selling off investment or assets, an increase of which would impact people with second homes.

The standard amount of profit that can be made without tax £3,000.

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Then, above this threshold, people are taxed somewhere between 18 per cent and 24 per cent.

Raising this rate in line with income tax cause the levy to fall within bands correlating with 20 per cent, 40 per cent and 45 per cent.

Such a move, although controversial, would allow the Treasury to rake in £12billion each year, data from the Centre for the Analysis of Taxation showed.

The wannabe Prime Minister threatened there was room to assist high street business with a struggling economy by increasing taxes on warehouses, in an interview with LBC.

Ex-Health Secretary Wes Streeting has previously called for CGT to mimic income tax.

Meanwhile, Louise Haigh, one of Mr Burnham's most loyal allies, called for CGT, along with inheritance tax, to be boosted so the Government can spend more.

Ms Haigh keenly advocated for a "deliver a meaningful economic renewal" through "a fundamental redesign of the UK tax system is required".

She added: "No more tinkering round the edges, but a full-scale reform agenda."

Ms Haigh quit from the frontbench last year after it was revealed she pleaded guilt to a fraud offence in 2013.