The coalition until now has been happy to adopt Paul Keating as a fellow traveller on economic reform.

Corporate tax cuts the former Labor prime minister implemented during his time in government have been used to bash today's opposition over the head.

Now they say Mr Keating is just a Labor man backing its leader Bill Shorten.

Mr Keating entered the election campaign fray on Friday in typical blistering style, accusing The Australian Financial Review of misrepresenting his track record.

"The AFR has embarked upon this campaign in collusion with the Business Council of Australia, in the council's camouflaged attempt to reduce the rate of company tax on foreign shareholdings," he wrote in a stern letter.

Do you believe the company tax rate should be cut? Yes 4709 No 5595

"The AFR must be alone among national financial newspapers in urging so massive an impost on the national fiscal balance."

Mr Keating argued his corporate tax cuts - from 49 to 33 per cent - were paid by a massive broadening to the tax base including through capital gains and fringe benefits taxes.

The Turnbull government, on the other hand, was proposing a discretionary unfunded tax cut of $50 billion.

"Tax reductions are desirable provided they are affordable," Mr Keating said.

In other words, not now.

Finance Minister Mathias Cormann, who has used Mr Keating's tax cuts to bolster the coalition's argument for its 10 year plan, played down the former Labor leader's intervention in the campaign.

"Don't look at what Paul Keating says eight days away from the election," Senator Cormann told reporters in Canberra.

"Look at what he did back in 1993."

Senator Cormann said it was hardly a news flash Mr Keating was a Labor man and was supporting Mr Shorten.

Mr Shorten, campaigning in Darwin, said the coalition invoking Mr Keating's name was a spurious and dishonest attempt to make the prime minister look "Keatingesque".

"He's said everything Malcolm Turnbull is doing about the way he's doing the corporate tax cut is wrong, wrong, wrong," the opposition leader told reporters.