The pop group will be the young face of the appeal, which raises money to aid former members of the armed services and their dependants.

The quintet, currently celebrating their third consecutive number one, will appear at the appeal's Youth Launch on London's South Bank this Sunday.

The British Legion has used high profile pop groups to promote the poppy appeal before. In 1997 their annual fundraising efforts were given a boost by the Spice Girls - who teamed up with wartime singer Dame Vera Lynn.

Old Spice: Dame Vera Lynn launched the appeal in 1997

"We feel very honoured to take part in this year's poppy appeal and hope that our contribution will be as momentous as the Spice Girls," said a statement from the band.

"In our social climate the poppy appeal is as relevant today as it was when it first started 78 years ago in 1921."

The group - Mark Feehily, 19, Kian Egan, 19, Shane Filan, 20, Bryan McFadden, 19, and Nicky Byrne, 21 - will join the Queen Mother in promoting the charity drive. Their latest hit, Flying Without Wings, has made them the only boy band to top the chart with their first three singles.

"We are thrilled that, in addition to the support of the ever-popular Queen Mother, WestLife are helping the Legion to highlight how the appeal is relevant to young people," said the Legion's secretary general Ian Townsend.

The British Legion makes more than 30 million paper poppies each year, which are sold in the run-up to Remembrance Day.

Charity relies on poppy appeal

"The Legion reaches out to over 15 million people in Britain and more than 50% of our funds come from the poppy appeal," said Townsend.

With the two world wars fading into the distant past, the Legion is keen to take its message to young people.

The organisation estimates that three-quarters of 16-24 year-olds observe the two-minute silence to remember the war dead on 11 November.

Last year football clubs and celebrities such as Des Lynam and Arsenal manager Arsene Wenger helped the Poppy Appeal collect a record £17.5m.