The relationship between Ryanair and its 600 pilots has reached a new low after hundreds of the airline's pilots boycotted information meetings hosted by chief executive Mr Michael O'Leary in London.

The meetings were called to persuade the pilots not to join the British Airline Pilots Association (BALPA). Ryanair has warned those pilots who refused to attend that their actions could jeopardise their careers.

The orchestrated snub to the airline's controversial chief executive is part of an ongoing spat between Ryanair and its pilots over pay and working conditions. Some sources suggest that close to half of Ryanair's pilots have joined the British Airline Pilots Association (BALPA) and the Irish Airline Pilots Association and want the trade unions to represent their interests.

In a separate development, the European Transport Workers' Federation, which has been studying Ryanair's work practices, is preparing to launch a Europe-wide campaign against the low fares airline aimed at tackling staff pay and conditions.

Ryanair, which has staunchly battled to keep trade unions out of the airline, sent letters to each of the absent pilots stating that their failure to attend Mr O'Leary's meetings demonstrated "a lack of interest in developing their careers and securing promotion in Ryanair".

At the same time Ryanair's head of personnel in Dublin, Mr David O'Brien, reacted angrily to the distribution of an information flyer compiled by IALPA and BALPA and had them removed from the pilot's pidgeon holes.

He subsequently wrote to all of its Irish pilots to warn them that this campaign "has already put your careers at risk yet again". The letter went on to threaten that the airline would refuse to train Dublin-based pilots, many of whom are senior captains, to fly its new Boeing 737-800 fleet of aircraft and would bring in crews from Stansted to fly them. "This is not a rumour, it is now a fact," Mr O'Brien stated in the letter seen by The Irish Times.

Ryanair also suggested that if the pilots unions' campaign to recruit its pilots didn't end it would force the Irish pilots to pay to be trained on its new aircraft. Industry sources estimate this could cost each pilot as much as €35,000.

Yesterday Ryanair said it did not comment on any internal communications or discussions between the airline and its staff. "Ryanair recognises the right of all its people to join any organisation of their choice," the statement added. Mr Brady had previously told the pilots that they might as well "join the Taliban" as join BALPA.

In a circular briefing their members at Ryanair BALPA said the reaction of those who attended the meetings found the chief executive's "choice of language" particularly negative. Sources close to the airline said that Mr O'Leary was incensed by the pilots' boycott.

IALPA president Captain Evan Cullen said yesterday that it had received a large number of new membership applications from Ryanair pilots since this correspondence was issued. "Many have been angered by the implied threats contained in those letters," he said. "We fully intend to act on the directions we are given by our members."

Ryanair pilots work close to the maximum hours allowed under aviation regulations and, as they are paid for each sector they work, tend to enjoy high earnings. Their take-home pay has been reduced by Mr O'Leary's cost-cutting measures which has led to pilots paying for their routine medical examination and their uniforms on top of their training costs. The airline has also frozen their existing pensions and does not provide pensions for new recruits.

In 1998 a bitter stand off between Ryanair and SIPTU triggered the closure of Dublin airport and left Mr O'Leary pledging that Ryanair would never tolerate trade union's representing its employees.

Speaking in London yesterday Mr O'Leary said that soaring oil prices may cost it an extra €40 million this year, but continued to rule out introducing a fuel surcharge. He said he was confident the price of fuel would fall in the next year and reiterated there were no plans to resume hedging until oil neared $30 a barrel.