Senior military figures have expressed concern about the security arrangements for a recent trip by David Cameron to Afghanistan.
The prime minister had to change his schedule at the last minute because of fears the Taliban might be planning to attack his helicopter.
It is reported that Number 10 has been asked to carry out a security review.
A Downing Street spokesman said: “We never comment on the prime minister’s security arrangements.”
BBC defence correspondent Caroline Wyatt says military sources were concerned over the threat to Mr Cameron during his first visit as prime minister to Helmand province in southern Afghanistan in June.
Mr Cameron was forced to abandon a visit to British troops serving at the front-line patrol base at Shahzad because of fears the Taliban were planning a possible attempt to bring down his helicopter.
The RAF Chinook carrying the prime minister and his entourage was instead diverted to the main operating base in the capital of Helmand, Lashkar Gah, at the last minute.
Mr Cameron had visited Kabul first, holding a media conference with Afghanistan’s President Hamid Karzai, before going on to Helmand.
Military sources have expressed their concerns over a number of security issues, not least that Mr Cameron was seen on television in the Afghan capital ahead of a visit to a combat zone They want to avoid similar risks on future trips.
In the past, visits to war zones by senior politicians and officials have often been subject to news blackouts until nearer the end of the trip, as was the case with the recent journey by Defence Secretary Liam Fox.
Mr Cameron had been due to meet the 1st Battalion Duke of Lancaster’s Regiment, but the Times newspaper reports Nato intelligence services intercepted telephone calls suggesting the Taliban were planning an attack.
The information was received within five minutes of the take-off of Mr Cameron’s Chinook, and the pilot was ordered to change course.
Earlier this year, police concerns about Mr Cameron’s security were reported over the prime minister’s insistence on walking around Whitehall and refusing motorcycle escorts.
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