Travellers should refrain from taking aspirin in the hope of avoiding blood clots associated with flying, experts said yesterday. Instead, airlines should be forced to give passengers more room to stretch their legs under a proposed change in flying rules.

A parliamentary committee called for the minimum space between seats to be increased by “at least two inches” for health reasons. But contrary to previous advice, travellers should not take aspirin to prevent blood clots during a long-haul flight, as the risks outweigh the benefits, doctors said.

The all-party Lords Science and Technology Committee recommended that the minimum distance between seats be increased from 26in (66cm) to 28.2in.

Lord Patel, a member of the committee, said that there were concerns that some seats were too small for passengers to adopt the brace position in an emergency. The changes would mean easyJet, Thomas Cook, Thomsonfly, Monarch Airlines, bmibaby, First Choice Airways and My Travel having to increase the leg room between some of their seats.

Cramped seats could also increase passengers’ risk of developing venous thromboembolism (VTE), which occurs when a blood clot or deep vein thrombosis (DVT), in a leg vein travels through the body to the lung, where it becomes lodged and blocks blood flow. This is known as pulmonary embolism, and symptoms include chest pain and breathing difficulties. If untreated it can be fatal.

The risk of developing VTE remains relatively low, at about 1 in 6,000, but findings indicate that the risk approximately doubles on any journeys lasting four hours or more.

The report shows that a number of other factors increase the risk of VTE during travel, including obesity, being taller than 1.9m or shorter than 1.6m, or for women, taking the Pill or hormone replacement therapy.

About one in five passengers takes aspirin before or after a long-haul flight, following evidence that it can help to prevent blood clots after surgery. But William Toff, Professor of Cardiology at the University of Leicester, told the committee: “Anyone who is at particular risk might like to consider other interventions, but for the average traveller the use of aspirin is a relatively ineffective in the prevention of blood clots.” He said that up to 24,000 people would have to take the drug in order to prevent one DVT. “On the other hand, the number that you need to treat for harm from aspirin is in the region of one in 17,000.”

The report called on the UK Civil Aviation Authority “to implement their own research” and increase the regulatory minimum distance between seats on commercial aircraft from 26in “to at least 28.2in”.

Airlines talk in terms of “seat pitch” about how much room they provide but the committee said that some airlines included the width of the back of a seat (typically an extra 2in) in this measurement. The committee expressed alarm at reports from union chiefs that pilots, particularly those who work for budget airlines, may be suffering from such severe fatigue because of work hours that they could be putting passengers’ lives at risk.

A spokesman for Monarch Airlines said: “We will look carefully at the published recommendations.” EasyJet said it had Europe’s most modern fleet, and Thomsonfly and First Choice said: “If the Civil Aviation Authority intends to review the distance we will assist.”

Both Thomsonfly and First Choice claimed to offer “more legroom in long-haul economy flights than Virgin Atlantic and British Airways”.