Shares in the UK's biggest holiday firm, MyTravel, have plummeted after its second profit warning in four months.

As largest shareholder in this group they have my total support

David Crossland Airtours chairman

At the close of trade the company's shares were 36% lower at 81.5 pence.

The shares fell after the firm said a change in the way it accounted for revenue from insurance policies would reduce this year's profits by as much as �15m ($23.5m).

But the chairman and founder David Crossland denied that the company was starting to look "accident prone".

And he defended chief executive Tim Byrne and his executive team.

"As largest shareholder in this group they have my total support," Mr Crossland said in a conference call.

Profits already squeezed

MyTravel, which used to be called Airtours, has seen business slow following the September 2001 terrorist attacks on the United States.

The company's shares plunged by a quarter in May after it said it still had one million summer holidays to sell.

Mr Byrne said almost all of these holidays had now been sold, but at slightly lower than expected prices.

Even before the accounting changes, the Rochdale-based company had been heading for a profit of about �105m for the year to the end of September.

That was as the lowest end of city expectations.

MyTravel portrays itself as a one-stop shop for holidaymakers.

It runs 1,000 shops, more than 100 hotels, four airlines and four cruise ships.

It launched its own budget airline last month.