BORIS Johnson and Rishi Sunak have put on a united front as they double down on April's National Insurance tax hike.

There has been speculation about the relationship between the two men in recent weeks as debate around Johnson's future continues. 

Sue Gray's "partygate" report is still to be published and when Johnson appeared before MPs to issue his apology over Downing Street gatherings, Sunak was not by his side.

Recent polling also found almost half of Conservative Party members think Sunak would be a better Prime Minister than his boss.

Commentators had named him as a leading candidate to succeed Johnson, if he is forced out of office.

But they've co-authored an article in the Sunday Times defending their plan for an NI rise in April.

The National:

Johnson was reportedly rethinking that policy in light of pressures on his premiership, with some Conservative backbenchers calling for it to be delayed.

SNP shadow Chancellor Alison Thewliss MP says the decision will have a "devastating impact on the lowest earners in society".

But Johnson and Sunak wrote that the Government "must go ahead" with the plan to fund Covid recovery.

They stated: "We are tax-cutting Conservatives. We believe people are the best judges of how to spend their money. We want to get through this phase and get on with our agenda, taking advantage of our post-Brexit freedoms to turn the UK into the enterprise centre of the world. We want lighter, better, simpler regulation, especially in those new technologies where the UK excels. We are Thatcherites, in the sense that we believe in sound money. There is no magic money tree.

"The only reason we were able to protect families and businesses during Covid was that we had been responsible with the public finances. We will take the same responsible approach to our recovery plan, from tackling the cost of living to fixing the backlogs. We will tackle our problems with the same dynamism that we brought to the booster rollout. With healthy finances we will continue to drive business confidence, and with record investment we will lay the foundations for a sustained, long-term, jobs-led recovery."

Thewliss, whose Glasgow Central constituency includes some of the worst-off areas in Scotland, said Tory ministers are "too mired in sleaze and scandal - and trying to save their boss's skin" to see the impact of the cost on living crisis on households.

The National:

She said: "The UK Government's decision to plough ahead with this regressive tax hike in the middle of a cost of living crisis is fundamentally wrong. 

"We know that the Tories have never understood the difficulties working class households face, but to do this at a time when families face a toxic concoction of Tory cuts, soaring energy bills and the growing cost of Brexit is cruel and callous.

"There is no doubt that this UK Government are completely out of touch with the reality of the cost of living crisis."

The increase of 1.25p per pound will see workers earning £20,000 pay out another £89 from their salaries and cost another £214 for those on £30,000.

Workers earning les than £9880 a year will not have to pay NI and so will be unaffected by the new rate.