Travellers face losing all their Airmiles if they fail to collect at least one in the next six months, the firm behind the scheme has admitted.

Airmiles is writing to 1.7m customers who have not collected any in the last two years, warning their accounts will be closed if they miss the deadline.

The firm said the measure was covered by its terms and conditions.

But Simon Calder, the Independent's travel editor, said it was akin to banks closing savers' current accounts.

'Extensive research'

Under the loyalty scheme, shoppers collect Airmiles when they purchase goods and services, and can redeem them as flights.

Some six million people in the UK hold an account, but the company admitted it had set a time limit in January.

The 1.7 million customers who will receive a letter from the firm have all accrued more that 500 Airmiles but failed to collect any more in the past 24 months.

Mr Calder told the BBC: "That's a bit like having a bank account where you're told, 'Ah, well, you haven't put any money in it for a couple of years so we've closed it down and kept your money.'"

But a spokeswoman for the company said that a major television advertising campaign about the benefits of the scheme had been launched, and insisted that the majority of members who regularly collect Airmiles did not have to do anything.

She said thousands of customers had responded by collecting Airmiles again.

"It is our intention that we will not close their account unless they have been communicated to, either via our web site, our UK Customer Contact Centre, our partner channels, or other ways of communication," she said.

"However, our extensive research has shown that these members are extremely unlikely to engage back into the scheme."