An emotional letter to parliament from the Belgian king’s wayward brother, in which he claimed he was the most exploited man in the country, has been dismissed by MPs who have fined him 15% of his endowment after a series of embarrassing incidents.

A three-page appeal for clemency by Prince Laurent, younger brother to King Philippe, was read out by the Speaker of the House on Thursday, before a vote on the sanction.

The government had proposed a reduction in the prince’s €308,000 (£280,000) annual endowment in response to his unapproved appearance, in full naval uniform, at a ceremony to mark the 90th anniversary of the founding of China’s People’s Liberation Army.

In his letter to the MPs, the prince, 54, told how he lived a life of service to the state and the royal family, who he claimed had hindered all his efforts to gain financial independence. “I even had to get permission to get married, and even today I pay the price for choosing a woman I love, without title or fortune,” Laurent wrote.

“I’m not free from mistakes, and I’m the first aware that people far more poor than me suffer a worse fate. But I do not think that any other citizen of this country has been, with his life, used with such relentlessness, and his projects constantly hindered by his family and by serious failures of some political leaders.”

Laurent claimed he had been remorselessly and unfairly traduced during his life over a “list of blunders, mistakes, mistakes, constantly longer over the years, constantly more overwhelming”, to which he had never been given a right of reply.

“Do I need to remind you that neither I nor my family is covered by social protection (healthcare, disability, pension)?” Laurent told MPs.

Of the reduction to his stipend, Laurent said the vote was “the trial of his life” and an unfavourable decision would “likely cause me serious prejudice, and be difficult to repair”.

Belgian MPs were unmoved by the appeal, and voted in the early hours of Friday morning by 93 to 23 votes in favour of withdrawing €46,000 (£40,340) of the prince’s allocation.

Patrick Dewael, an MP for the Flemish Liberals and Democrats party, said: “It is a deduction from a donation, not a penalty. Princes and princesses are not obliged to apply for a grant.

“If they do, they have a duty to respect rules. I would like to ask that the prince does not turn too much into self-pity.”

Laurent’s appearance at the Chinese embassy in Brussels to celebrate the founding of the Red Army last year might have gone unnoticed had he not tweeted a picture of himself at the ceremony.

His previous diplomatic freelancing has involved jetting off to see President Joseph Kabila of the Democratic Republic of the Congo, who refused to step down at the end of his mandate in December 2016.

The prince, who likened his family to the Stasi in 2015, also enjoyed frequent visits to Libya between 2008 and 2010, where he had been hoping to go into business with one of Muammar Gaddafi’s sons.