Kym Marsh reportedly cheated on her husband with 'Coronation Street' co-star Oliver Mellor.

The 37-year-old actress married Jamie Lomas in September 2012, and it is said her secret affair with the soap star began five months after the wedding.

A source told The Sun newspaper: ''Kym was terrified of being found out so she and Oliver only went out in public together a few times.

''They both knew it was wrong because Kym had only just got married - but they just couldn't resist each other. The chemistry between them was just too strong.''

The couple's fling started after they filmed scenes for the soap in which Oliver - who plays Doctor Matt Carter - was performing a ''striptease''.

The insider added: ''They were doing loads of scenes together around the time of the Rovers [Return] fire, when Oliver's character was doing a striptease with some others at Nick's bistro.

''Oliver definitely caught Kym's eye during the striptease - they were eyeing each other up all night during those scenes.''

Things escalated after a ''cast night out'' when Kym's husband was in the US trying to reignite his own acting career around Valentine's Day.

The source said: ''There was a cast night out around Valentine's Day. Jamie was away in America and Kym felt lonely and desperate for attention.

''The chemistry was building and building. Kym is one of the sexiest women on TV and Oliver was loving every minute.

''He was very attracted to Kym physically and used to text her. He definitely had feelings for her.''