David Cameron has not yet persuaded British overseas territories that operate as tax havens to send representatives to his international anti-corruption summit in London this week.

With only days to go before the meeting, Downing Street said it was still “in discussions” with overseas territories and UK crown dependencies about their attendance.

UK overseas territories, including the British Virgin Islands and the Cayman Islands, were at the centre of the shadowy tax avoidance networks uncovered by the Panama Papers.

The Prime Minister has been already criticised by tax campaigners over the Government's failure to secure agreements from UK territories requiring them to create public registers of company owners – a move that would bring transparency and allow scrutiny of the kind of shell operations used by tax avoiders, and has been brought in the UK itself.

Thursday’s summit, which was organised before the Panama Papers leaks, will be attended by world leaders including the presidents of Afghanistan, Colombia and Nigeria, and the Prime Minister of Norway, Downing Street said today.

The Government was reported to be struggling to persuade other leaders to attend the summit, and has also faced accusations that key pledges – including an international call for fully public registers of beneficial ownership, had been watered down. The Times reported that successive drafts of the summit communiqué seen by the newspaper had key passages cut from the text, including one supporting the work of the media in exposing tax avoidance.

The discouraging signs will be a disappointment for Mr Cameron, who may have harboured hopes that the summit would showcase his commitment to tackling tax avoidance, following revelations about how he benefitted in the past from an offshore company established by his father in the Bahamas.

Speaking ahead of the meeting, the Prime Minister said: “Corruption is an enemy of progress and the root of so many of the world’s problems. It destroys jobs and holds back economic growth, traps the poorest in desperate poverty, and undermines our security by pushing people towards extremist groups.

“The battle against corruption will not be won overnight. It will take time, courage and determination to deliver the reforms that are necessary. But we cannot hope to solve the major global challenges we face without tackling the exploitation, fraud and dishonesty at their heart.