Carol Garside, 48, of Holton-le-Clay, Lincs wept as she was taken from the dock at Lincoln Crown Court to start a nine month prison sentence.

Having co-habited with another man after the death of her first husband and later remarried, she was not entitled to the War Widows' or Armed Forces' Pension she claimed between 1993 and 2011.

An anonymous tip-off led Ministry of Defence investigators to check her claims over the previous 18 years following her co-habitation and eventual marriage to a fireman Andrew Garside.

She admitted a total of four offences, including obtaining money by deception by failing to admit she was living with another man.

She also admitted fraud and failure to disclose her new domestic situation. The court heard there will be Proceeds of Crime proceedings against Garside later this year to force her to repay the money.

Sentencing Garside, now a married mother-of-two, Judge Sean Morris said: "Over many years you were defrauding the Armed Forces Pension Scheme. That amounted to nearly £145,000. That is a considerable sum."

He added that benefit fraud offences are "easy to commit" but "cost the country a fortune. When people are found to have committed fraud, in order to discourage others, there has to be a deterrent," added Judge Morris.

"This was deliberate fraud and for a considerable period of time you had a better standard of living."

Relatives in the public gallery gasped as the sentence was passed down and Garside clasped her mouth and said: "Oh God. I didn't do it on purpose. What about my children?"

Chris Geeson, prosecuting, said a total of £143,943.79 had been fraudulently claimed because she had failed to declare her co-habitation.

He said the widow had been repeatedly asked in letters sent by the MoD each year, whether there had been any change to her circumstances.

In interview, she said she had not read any of the letters or terms and conditions of the pension payments. Mr Geeson said it had been an "anonymous tip-off" which started the investigation.

Shortly after MoD officials sent her a letter in March last year, she announced her marriage to fireman Mr Garside and they got married on April 23 last year.

Representing Garside, Terry Boston, said his client married Michael Thomas, a Royal Navy serviceman, in 1984. Three years later he was tragically killed in a road accident. A friend of theirs had also died.

He said his client was in a confused state at the time and never had any intention of defrauding the Armed Forces. He said she assumed she was entitled to the pension unless she remarried.

Mr Boston added: "She accepts that papers were sent to her and she ought to have known. She accepts she was dishonest. "She felt sick to the stomach with guilt . She was not trying to hide that they were living together. They have two children, bills are paid together. She is fearful of custody but the greatest punishment is the guilt and shame she is feeling."

Garside had offered £400-per month to pay back the money she had taken, he said.