The brother of Ken Bigley says he lost two days of his campaign for the Iraq hostage's release when intelligence officers sought evidence at his home.
Videos of Mr Bigley have been broadcast on Arabic television
Paul Bigley said UK and Dutch officers visited his Amsterdam home and copied computer files relating to his dealings with contacts over the kidnapping.
"I lost two days... I was preoccupied," Paul Bigley told BBC News 24.
But a Foreign Office spokesman said:
"No British officials of any kind have raided Paul Bigley's home."
The PA news agency said the officials were simply police family liaison officers.
It is understood they may have looked at e-mails Mr Bigley said he had received from around the world to see if there was anything that could help in the ongoing efforts to secure his brother's release.
Dutch public prosecutors' spokesman Wim de Bruin said: "We worked with the British police to put them in touch with Mr Bigley. It was done on a voluntary basis.
"Anything the British police took away with them was on a voluntary basis."
Ken Bigley and two American colleagues were taken hostage in Baghdad on 16 September by the Tawhid and Jihad group, headed by al-Qaeda suspect Abu Musab al-Zarqawi.
The two Americans have since been beheaded.
Mr Bigley, a 62-year-old engineer from Liverpool, has been shown in two videos - the latest broadcast on Arab television station Al-Jazeera on Wednesday - pleading for UK Prime Minister Tony Blair to save him.
Paul Bigley denied having any contact with the kidnappers as part of his efforts to secure his brother's freedom.
"I had nothing to hide," he told BBC News 24.
"Of course I would co-operate with the authorities - that is the first thing that any good citizen should do. I did that.
"But there are ways of going about these things.
"I lost two days of my campaign for this, but I totally understand what they are doing - they are simply trying to find the baddies.
"I shall be campaigning tomorrow morning."
More than 100,000 leaflets from Ken Bigley's family pleading for his release were distributed in Baghdad on Friday.
It was the second time such leaflets have been distributed in the city, with 50,000 being handed out by the British Embassy last week.
British Muslim leaders also appealed to Mr Bigley's captors in the pamphlet, saying the kidnap was not consistent with the Islamic faith.
The Bigleys' message for the Liverpool engineer read: "We love and need him".
The group holding Mr Bigley has reportedly demanded the release of women prisoners held in Iraq.
The International Committee of the Red Cross
said on Friday that Britain did not hold any women
prisoners in Iraq, and said it was ready to act as a
mediator to help free Mr Bigley.