Alfonso Merlos was unaware that he had been 'busted' when eagle-eyed viewers noticed the semi-clad woman was not his girlfriend.

A Spanish news anchor dating a 'Big Brother' star has been called a love cheat after a different woman was spotted behind him while he was live on air at his home.

Alfonso Merlos was unaware that he had been 'busted' when eagle-eyed viewers noticed the semi-clad woman was not his girlfriend Marta López as he spoke to a host on the Estado de Alarma channel during a video call on YouTube.

She was later identified as 27-year-old journalist Alexia Rivas after a national scandal broke out and he was accused of cheating and the pair were claimed to have broken Spain's strict coronavirus social distancing measures to have their fling.

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The 41-year-old remained silent for days before insisting his relationship with Marta had ended before he was caught with Alexia.

Alfonso went on to apologise to Marta for any hurt he caused during an appearance on the Ana Rosa show - a Spanish chat show.

He said: "If you think that my attitude has not been correct or that there are things that I have not done well.

Alfonso Merlos with his ex Marta Lopez. Photo:PA Images.

"I have no problem asking for forgiveness, although my goal was not to harm someone else."

Alexia has claimed she had been seeing Alfonso for several weeks before she was caught on camera.

She told Socialité: “I didn't get into a relationship, he told me he was single. We have been (seeing each other) three weeks.”

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But Marta said they were a couple at the time calling the incident “unpleasant” and “shameful”.

According to Spanish news outlet Lecturas, the couple had rowed over an ex-boyfriend of hers, who she has a son with, and they spent four days apart during which the broadcast occurred.

Marta told them: "I had been mad at Alfonso for four days. He didn't want me to do something that affected my family. I did it, and he got mad. "

Alexia Rivas said she had been seeing the news anchor for several weeks. Photo: Getty Images.

She also claimed they had been in coronavirus lockdown since March 12, two days before Spain introduced some of the world's strictest measures, until their argument.

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Spain is one of the countries worst hit by COVID-19 with more than 235,000 confirmed cases and more than 24,000 deaths.

People have been banned from going outside for anything other than the essentials since March 14.