Judy Murray has revealed her tennis champ son Andy thinks she will be a Strictly Come Dancing disaster - and will cringe with embarrassment if he has to watch her.

The sports coach said the famously taciturn 2013 Wimbledon men's champion did not exactly welcome her inclusion in the line-up of contestants, telling her she would be "terrible".

She is one of 15 celebrity competitors who will be seen making their dancefloor debuts on the launch show on Sunday as the series lines up against its ITV rival The X Factor for the annual ratings battle.

Murray, who is 55 on Monday, has long been a fan of the series and has already taken the training to heart by drilling her routines at every available opportunity.

The mother of two - whose other son Jamie is also a tennis pro - said she got a mixed reception from her boys when she told them she was considering the programme. But she is expecting Andy to go to the studio to support her as "payback" for the years she has spent watching him from the stands.

She explained: "When I told the boys that I might do it - I didn't know if I would do it because you have to give about three and a half months of your life away to it and because I travel a lot and with my job, I didn't know if I would be able to. And when I said to Jamie, he said 'oh mum, you'll love that, you love that show' and Andy said 'oh my god, you'll be absolutely terrible'."

Asked if Andy would be attending the live shows, Murray said: "I think he will if he's at home. I can see him taking a seat on the back row and slowly sliding underneath the chairs - but I've said it's payback time."

She has been working hard on the opening routine which will be showcased in Sunday's show and drawing on her own experience of training others.

"I know how to train people as a coach so I know the whole 'repetition being the mother of skill' and all the rest of it, so when I was spectacularly bad the first two days, I went off to HMV on Saturday morning and bought the CD that had the track on that we had to dance to, got it on in my kitchen, got the high heels out cos we got a wooden floor and I was dancing to my heart's content in my kitchen and I feel a whole lot better."

Murray went on: "I went to Gleneagles to the country club and it's got a hot pool and a steam room and I was actually in the steam room doing the routine by myself until I got far too hot and had to get out - so it does take over."

She will be up against figures such as Bargain Hunt presenter Tim Wonnacott, singers Pixie Lott and Frankie Bridge, TV adventurer Steve Backshall, Radio 1 DJ Scott Mills and EastEnders actor Jake Wood.

Murray is often seen looking fierce as she urges on her son from the stands but says she will take it in good humour if things don't go well

"If I'm terrible, I'll just laugh - because you have to," she said.

Strictly has taken the lead over X Factor in the ratings in the past two years but ITV has been hoping for a boost in fortunes with a return to the judging panel for Simon Cowell and Cheryl Fernandez-Versini - formerly Cole.

But after a promising start on Saturday for the launch show which drew 9.5 million viewers, it had slipped 8.2 million the following night - which is 1.7 million fewer than the equivalent edition of X Factor last year.

Strictly's launch on Sunday goes directly head to head with the singing contest, with both shows beginning at 8pm.