A WATFORD company selling £5 commemorative coins marking the Queen Mother's 100th birthday has been criticised for claiming it 'may be your only opportunity to own one'.

The Advertising Standards Authority (ASA) upheld a complaint against Westminster Collection - a coin and stamp dealership which has offices in Rickmansworth Road, Watford - regarding an advertisement it placed in national magazines in February.

It ruled the company, trading in Watford for more than 50 years, implied the coin was not available from other sources.

An ASA spokesman said: 'Because that was not true, we concluded the advertisement was misleading.'

The company was asked to amend the advertisement.

Admirers of the Queen Mother, who will be 100 on August 4, can buy the high-quality coin from the Royal Mint and other dealers, as well as Westminster Collection.

Mr Ian Glen, Westminster Collection's marketing director, said the company agreed to amend the advert as soon as ASA notified them of the complaint from a member of the public.

He said it appeared in one or two publications once, and referred directly to an exclusive 50,000 limited edition, which includes the coin and a commemorative millennium stamp in a special presentation pack, costing £9.99.

Mr Glen said: 'There wasn't enough clarity in the wording. It was a minor thing and we corrected it straight away. I know of no complaints from our customers.'

The Royal Mint first announced details of the centenary crown in January.

The coin has a portrait of the Queen Mother on one side by sculptor Ian Rank-Broadley, with her signature, the dates 1900 and 2000 and a flag-waving scene.

His portrait of the Queen is on the other side.

A spokesman for the Royal Mint said : 'Limited editions in gold and silver will be available at the end of May and a circulating version will be available in August.'

The latter will be available at face value from the Royal Mint, dealers, banks and post offices.

A spokesman for the Queen Mother at Clarence House said it was too early to discuss other plans to commemorate her special birthday.

But she said it was likely commemorative stamps, china and glass goods would become available.