Katie Hopkins instructed her legal team to “sling mud” at the food writer Jack Monroe while they defended her in court from accusations of libel, a strategy for which she should “pay the price”, Monroe’s barrister has said.

Closing his submissions on the third and final day of the defamation hearing against Hopkins, William Bennett told the high court in London that the controversial columnist had never apologised for two Twitter messages she directed at Monroe in May 2015, which allegedly implied that the blogger had defaced or supported defacing war memorials.

Monroe argues that the tweets are libellous, have caused serious reputational harm and led to death threats from other Twitter users.

The judge, Mr Justice Warby, has reserved judgment in the case until later this month.

The dispute between the two writers originated as a case of mistaken identity when Hopkins, who writes for Mail Online, messaged Monroe: “Scrawled on any memorials recently? Vandalised the memory of those who fought for your freedom[?] Grandma got any more medals?”

The court has heard that Hopkins had confused the food writer with Laurie Penny, a columnist for the New Statesman who had earlier tweeted that she had no objection to the recent defacing of a war memorial as part of an anti-austerity protest.

Monroe replied to Hopkins: “NEVER ‘scrawled on a memorial’. Brother in the RAF. Dad was a Para in the Falklands. You’re a piece of shit,” and sent further tweets requesting an apology or retraction.

Hopkins deleted the original tweet two hours later, but posted a second, which read: “Can someone explain to me – in 10 words or less – the difference between irritant @PennyRed and social anthrax @MsJackMonroe.”

Bennett told the court: “We say the second tweet was published as an act of defiance against [Monroe] … It was absolutely obvious to the defendant … that the complainant absolutely abhorred the behaviour being ascribed to her.”

He disputed the argument of Hopkins’s legal team that the first message had merely been part of a heated political debate – “We say there is no political message in that tweet” – and rejected the defence’s argument, advanced earlier, that “people don’t believe what they read on Twitter, that somehow Twitter is the wild west”.

“Even if Twitter is the wild west, which we dispute, that doesn’t exclude it from the operation of the law. Even the wild west had local marshals to ensure people weren’t bullied.”

The court was told on Tuesday by Hopkins’ barrister that the claim was part of a “crusade” against the columnist, and that Monroe was an equally provocative voice on Twitter who used “an arsenal of dirty insults” to express outrageous political views “publicly, aggressively, on an almost daily basis”.

Bennett said he believed the defence lawyers had conducted the case professionally, “but they are acting under instructions – the instructions of Katie Hopkins”. Those instructions, he said, were “to throw mud at the complainant and rake up stale allegations … that we say are wholly irrelevant to the court’s decision”.

He added: “As with any libel case, a defendant ought to pay the price of running that sort of strategy during a trial.”