The UK’s ambassador to Portugal, Alexander Wykeham Ellis, told his American counterpart that police in Britain were working with Portuguese officers to build a case against the McCanns.

He made the claims on September 21, 2007, according to secret diplomatic cables published by WikiLeaks.

Tough times: Kate and Gerry McCann were subject to a Portuguese police investigation, allegedly aided by evidence 'developed' by their British counterparts

Two weeks earlier, Portuguese police had named Gerry and Kate McCann as ‘arguidos’, or formal suspects.

In a cable to Washington marked confidential, U.S. ambassador Al Hoffman wrote: ‘Without delving into the details of the case, Ellis admitted that the British police had developed the current evidence against the McCann parents, and he stressed that authorities from both countries were working co-operatively.’

The cable does not specify what evidence British police are alleged to have gathered, or whether UK investigators were involved in the decision to formally name the McCanns as suspects.

The comments suggest British police had a far greater role in the investigation of the McCanns than has previously been thought.

The widespread perception at the time was that Portuguese authorities were the driving force behind their treatment as suspects.

Missing: Madeleine McCann disappeared while on holiday in Portugal

In one of two cables which refer to the case, U.S. ambassador Hoffman also noted: ‘Madeleine McCann’s disappearance in the south of Portugal in May 2007 has generated international media attention with controversy surrounding the Portuguese-led police investigation and the actions of Madeleine’s parents.’

He said the British ambassador thought ‘the media frenzy was to be expected and was acceptable as long as government officials keep their comments behind closed doors’.

The McCanns have said that there was ‘absolutely no evidence to implicate them in Madeleine’s disappearance’.

After they were named as suspects, Madeleine’s parents remained under official suspicion until July 2008, when Portuguese police shelved the investigation into their daughter’s disappearance.

Speaking when their suspect status was lifted, Mrs McCann said: ‘It is hard to describe how utterly despairing it was to be named arguidos and portrayed in the media as suspects.’

Following the WikiLeaks revelation, a spokesman for the McCanns said: ‘This is an entirely historic note that is more than three years old.

‘Subsequently, Kate and Gerry had their arguido status lifted, with the Portuguese authorities making it perfectly clear that there was absolutely no evidence to implicate them in Madeleine’s disappearance.’

Madeleine went missing from an apartment in the Algarve village of Praia da Luz on May 3, 2007, when she was three years old.