Peter Kay and Tony Christie will storm to number one this weekend.

Their version of (Is This The Way To) Amarillo for Comic Relief looks set to sell 150,000 copies in its first week.

A delighted Peter said: "It's unbelievable and a hell of an achievement. It looks set to raise a lot of money and make a lot of people laugh. I bet 21,000 copies were sold in Bolton alone on the first day it was released. I can't thank everybody enough for their support."

An hilarious video which shows Peter and a host of celebrities marching and miming to the song has made the catchy tune even more popular.

It will be officially crowned the UK's top selling single on Sunday.

The last time Amarillo hit the top of the charts was in 1971 in Spain.

In Britain it reached number 18. The single was released on Monday after the video was first shown on Comic Relief last Friday.

Peter, who was recently voted Britain's favourite comic, has used Amarillo in his stand-up routines and TV show Phoenix Nights.

Nationwide, it sold 40,000 copies on Monday, according to first-day sales figures from retailer HMV, and on Wednesday another 25,000 sales were registered.

HMV spokesman Gennaro Castaldo said that the official Chart Information Network music charts showed that the race was over.

"The single is still outselling the number two song by two to one," he said.

"At this rate, it seems certain to sell well over 150,000 copies in its first week

"There is no question. It will be number one this weekend by a distance."

Even bookmaker William Hill was certain of the outcome.

"We didn't even open a market on this one," said a spokesman.

"We knew how popular it would be, and we don't usually open markets on singles apart from Christmas, so we shied away from taking any bets at all."

A spokesman for Comic Relief said that the charity was "amazed and delighted" at the single's success.

"We can't thank Tony and Peter enough for this," she said. "Their contribution has been fantastic, and everyone in the video gave their time for free. It will certainly make a big impression on the final total."

A DVD version of the video single will be released on Monday.

The price is to be confirmed, but it is "very likely" that it will sell for £3.99, the same as the current enhanced CD. If projections are correct, the combined sales of both could add close to £1 million to the Comic Relief total, which is currently just under £38 million.

News of the single's success also delighted singer Tony Christie, who is in the middle of a mammoth UK tour on the strength of the song's revival. He visits the Albert Halls for a sell-out concert on March 31.

"That is fantastic news," he said. "It looks like everyone has taken the song to their heart and it's great to see it get to number one at last. I think it's a great song and deserves it. And it's great that so much money is going to be raised for such a good cause. The video was great fun on the day."

Tony had been living in Spain when the Amarillo avalanche began.

He said: "I watched the first series of Phoenix Nights at home in Spain. I couldn't believe it. I was absolutely taken by surprise. "My phone was red hot with people ringing up to see if I had seen it and it just seems to have snowballed. I spoke to Peter and it's just gone berserk for me since then."

Tony is no stranger to Bolton. He regularly performed to sell-out crowds at Farnworth nightclub Blighty's in the 1970s, and helped to switch on the town's Christmas lights last year. One of his biggest fans is Peter Kay's mother.

Tony's son and manager Sean said: "Peter told my dad that his mum used to play Amarillo to get him to sleep. Dad didn't know if it was a compliment or not!"