Lord Hanningfield, 70, who is being tried under his name Paul White, made various "false and misleading" claims for travel and accommodation expenses between March 2006 and April 2009, Chelmsford crown court was told.
"We will call evidence to establish that each one of Lord Hanningfield's claims for night subsistence was false," said prosecutor Clare Montgomery QC.
"He never stayed overnight in London at any stage during the period in the charges.
"On the vast majority of nights he went home to Hanningfield. On the few occasions he did not, he was not in London.
"He was variously on a plane bound for India or at hotels outside London, all paid for by someone else, mainly Essex county council.
"The majority of Lord Hanningfield's travel claims in each of the six months were false: either he did not make the journeys he claimed for, [or] if he did make the journey it was paid for by Essex county council."
Hanningfield is charged with six counts of false accounting covering six months of House of Lords expenses claims. He denies the charges.
Montgomery told the jury of nine women and three men that Hanningfield was not paid for his role as a peer but could claim expenses for travel and overnight stays in London.
The court heard Hanningfield claimed almost £155 per night for hotel accommodation and often claimed £15 for a first-class train ticket between London and Chelmsford and 40p per mile for a 15-mile trip between the train station and his home in the village of West Hanningfield, even though the journey was only 7.5 miles.
She told the jury that when Hanningfield travelled by train he normally paid for his ticket with an Essex county council corporate credit card. When he was chauffeur-driven, the council also picked up the bill, and if he went by taxi it was also paid for by the county council.
The court also heard that Hanningfield ran up an average bill of £5,200 a month – £170 a day – for "entertaining" at bars and restaurants in London, but one bill in May 2008 was "just under £10,000".
"The credit card was used, perfectly legitimately, to claim for entertainment, bar bills, hotels and travel," she told the court.
"The average claim was several thousands of pounds a month. This meant there was little or nothing that Lord Hanningfield had to pay out of his own pocket in relation to his own subsistence or expenses in the periods with which you are concerned."
The trial judge, Mr Justice Saunders, allowed Hanningfield to sit behind his team of lawyers instead of in the dock because the peer has hearing difficulties.
The judge earlier told reporters they could tweet about the case from inside the courtroom.
Hanningfield has been suspended from the parliamentary Conservative party and stood down as a frontbench business spokesman in the Lords and as leader of Essex county council.
He said at the time that the accommodation claims had been made in good faith. The trial, expected to last two weeks, continues.
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