Apprentice contestant Ruth Whiteley says being fired by Lord Sugar was "one of the worst moments of my life".

Alongside Selina Waterman-Smith and project manager Scott Saunders, Whiteley faced Lord Sugar in the board room after their team lost the pet product sales challenge. She received criticism from Lord Sugar for "zero" sales, despite her enthusiastic attempts to woo potential customers.

Lord Sugar said Saunders needed to be more "ruthless" when managing his team, adding: "I'm not using that as a pun, because maybe less Ruth would have been the best thing. So, Ruth, you're fired."

Looking back, the 47-year-old said: "It was one of the worst moments of my life. I was floored, I was surprised, and I was terribly personally disappointed to be leaving. It was a complete and utter surprise to me."

After a re-shuffle mixed up the boys and girls teams, Lord Sugar tasked the members of Connexus and Versatile with selling pet products to visitors at the London Pet Show. They were split into sub-teams, with one half obtaining and selling cheaper accessories, and the other focusing on a high-ticket item.

Versatile triumphed with animal balloons, animal T-shirts, and luxury pet beds, while losing team Connexus were flogging warming pads for cats, an LED cat toy, and customise-able cat beds.

Despite her chatty and enthusiastic attempts to persuade customers, Whiteley "had a bad day at the office" and was not able to close any sales - compared to three for Saunders and one for Waterman-Smith.

Whiteley, who has a background in telephone sales, recalled: "I knew I was up against it, and that's why at lunch time I took myself off into the toilet, I ran the tap, I looked in the mirror and I said: 'You are a superstar - go and make this happen! Oh my God, don't let it end today! Not with blinking cat towers.'

The fired contestant said she knew she was likely to face Lord Sugar when the Connexus team lost, because project manager Saunders - who had moved over from team Versatile alongside Gary Poulton and Brett Butler-Smythe - would never bring his two "best friends" back into the board room with him.

With Natalie Dean having had "a great day selling", this left Whiteley, Waterman-Smith, and their team-mate Elle Stevenson in the firing line.

Whiteley said: "For me, it should have been Brett and Gary. But from Scott's perspective, I think the only people he was ever going to bring in, was either going to be Elle, me, or Selina."

She added: "Truly, I thought Selina would go, but for the reasons really that Claude (Littner) outlined: her lack of enthusiasm and drive on the sales floor. So I just figured, as a sales person, that Lord Sugar would see that for what it was, and I thought that she would go... I know that I contributed so much more than Selina."

In the board room, Lord Sugar said: "Seems to me you couldn't sell a bone to Battersea Dogs Home at the moment, from what I've heard."

In his final summing-up, he added: "I don't dispute your enthusiasm, but you claim to be a salesperson, you claim to train people how to sell; here we are on a sales task and you failed miserably."

Reflecting back on the task, Whiteley said: "It was just the most frustrating day I've ever had. But it's been the biggest kick, and actually - bizarrely - it's been the biggest boost. Because I haven't had a day like that - I can't think of the last day I've ever had like that. But you need that sometimes. It's like a real smack round the face with a wet fish.

"And it made me think: 'Bloody hell Ruth, what is your offering, what are you doing?' And so actually it's really refocused me, it's actually driven me, and it's made me more determined than ever to succeed."

Whiteley was already known for her enthusiastic sales technique from the first episode.

Watching her successful attempts to sell fish lunches to office workers in the street - which included feeling a man's bicep - Karren Brady said of Whiteley: "She has a slightly creepy sales technique and is a bit odd in the way she approaches people. But it seems to be working."

But the fired candidate doesn't hold this against Lord Sugar's aide: in fact, she is proud of the remark.

She said: "Karren gave me that beautiful phrase, didn't she? 'Her sales technique is slightly creepy but it seems to be working!' You'd pay for that, wouldn't you? So that being fantastic forever, I shall love her for that, and for her ability to look good whatever the weather."

And despite Lord Sugar having fired her, Whiteley hasn't lost any respect for him.

She said: "I value his opinion. Christ! I've paid to read his book. So I am interested in what he has to say, and I don't dismiss his comments lightly. I take them on board. I think he's great. I think he's fabulous. I hate that index finger of his, that's the only bit about him I don't quite like.