The publication date of the long awaited Defence Investment Plan remains uncertain

Poland, a rising defence superpower, has told Britain to increase its defence spending or risk global irrelevance.

Radosław Sikorski, Poland's foreign minister, has urged the UK Government to publish a robust defence plan at Nato's upcoming summit in Ankara, Turkey.

He said: "If you want to be a global player, you need to back up your diplomacy with force.

"Britain has unique convening power, a global outlook, first-class intelligence and all that.

"But, when push comes to shove, you either have the ships to send to the Gulf or the brigades to deploy to Ukraine, or you don’t," he added.

The UK Government is yet to publish the Defence Investment Plan (Dip), which was due to be made public in Autumn last year.

Deputy Prime Minister David Lammy said on Monday the Government is planning to publish the Dip before July 7.

Britain is bracing for questions over its defence investment and commitments at the Nato summit in Turkey - a situation which has been made more complex by Sir Keir Starmer's resignation on Monday.

The lack of Britain's defence preparedness has sent alarm bells ringing throughout Europe's Governments, with Mr Sikorski’s criticisms reflecting a growing sentiment the UK is a dwindling military power.

Mr Sikorski, an Oxford-educated Anglophile, has seen his country become Nato's fastest growing military power.

Poland has more than doubled its defence spending since Vladimir Putin's invasion of Ukraine in February 2022.

The central European country will spend 4.8 per cent of its GDP on defence this year - the highest percentage of spend in Nato.

Nato members pledged last year to increase their defence spending to 3.5 per cent of GDP by 2035.

Britain is 1.4 per cent of GDP off this target - just over £40billion.

Former Defence Secretary John Healey resigned on June 11 over the lack of proposed investment in defence.

Mr Healey said in his resignation letter to the now-outgoing Sir Keir the Dip's current proposed funding was falling short, with only £13.5billion extra allotted to defence, leaving a £14.5billion shortfall of what is needed.

He wrote in his letter to Sir Keir: "This new era for defence required further investment through the Defence Investment Plan.

"The excellent and extensive cross-government work that completed in January – overseen by you, me and the Chancellor – confirmed the scale of the challenge and the rising demands on defence.

"Since then, you have been unable, and the Treasury has been unwilling, to commit the resources that the nation needs to defend the country at this time of rising threats."

Mr Sikorski echoed there was a similar sentiment to Mr Healey's in Poland's defence department.

He said: "When I was defence minister, we had a saying in our ministry that our first enemy is the finance minister."

He continued to say all Nato members need to remain committed to their pledges made in the Hague last year.

He said: "We now all have to do what we pledged ourselves to do at the Hague summit. We don’t need to do anything heroic – we just have to do what we declared we would do.

"Some countries risk falling foul of the Sikorski principle that ministers and heads of governments at Nato meetings should have one minute of speaking time for every one per cent of GDP their country spends on defence."