Bill O'Reilly has filed a lawsuit accusing his ex-wife of having an affair while the two were still married and demanding that she hand over $10million to the Fox News host.

In legal papers filed in Nassau County, New York and obtained by Gawker, O'Reilly claims that Maureen McPhilmy 'made false representations and material omissions of existing fact ... for the sole purpose of inducing Plaintiff to agree to a consensual divorce and to obtain money and real property to finance an existing extra-marital relationship.'

The couple separated in 2010 after 14 years of marriage and divorced a year later.

In March, McPhilmy was granted full residential custody of the pair's two teenage children, a 13-year-old son and 17-year-old daughter, after a prolonged custody battle.

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Back to court: Bill O'Reilly, 66, has filed a lawsuit against his ex-wife Maureen McPhilmy (above in 2002) accusing her of having an affair during their relationship

O'Reilly, 66, filed his lawsuit on April 1, asking that the case proceed in secret.

The court papers also state that McPhilmy, 50, had 20 days to respond or 'judgment will be entered by default for the sum of $10million.'

These papers were filed just one month after McPhilmy was awarded custody of the children following a four-year court battle during which testimony claimed that the couple's daughter had watched O'Reilly dragging her mother down a staircase in their home by her neck.

The Fox News host denied this allegation, calling it '100 per cent false.'

McPhilmy is now married to Nassau County Police detective Jeffrey Gross (above)

He later added in a statement; 'All allegations against me in these circumstances are 100 percent false. I am going to respect the court-mandated confidentiality put in place to protect my children and will not comment any further.'

After O'Reilly and McPhilmy separated in April 2010, she began dating a Nassau County Police detective named Jeffrey Gross - who she has since married.

Upon learning of their relationship, O'Reilly – who had previously raised money for the department – is alleged to have had an internal affairs investigation launched into Gross.

Then in March 2013, O'Reilly was accused of running a smear campaign against his wife of 15 years and even trying to ban her from the Catholic Church according to Gawker.

The news anchor allegedly told the church that his ex wife was receiving communion even though she'd been divorced and remarried and that she'd been telling their children that her second marriage was valid in the eyes of God.