As an ex-presidential consultant, a former adviser to the World Bank, a financial researcher for the United Nations and a professor in the US, Artur Baptista da Silva's outspoken attacks on Portugal's austerity cuts made the bespectacled 61-year-old one of the country's leading media pundits last year.

The only problem was that Mr Baptista da Silva is none of the above. He turned out to be a convicted forger with fake credentials and, following his spectacular hoodwinking of Portuguese society, he could soon face fraud charges.

Mr Baptista da Silva's conversion into the latest must-interview figure on the media circuit began when he turned up last April at Lisbon's main philanthropic institution, the Academia do Bacalhau, with a large supply of business cards – which, it later turned out, bore false credentials – and an impressive-sounding dissertation entitled Growth, Inequality and Poverty. Looking Beyond Averages which, it also transpired, was "borrowed" from its writer, a World Bank employee, via the internet.

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At the time, Mr Baptista da Silva also claimed to be a social economics professor at Milton College – a private university in Wisconsin, US, which actually closed in 1982 – and to be masterminding a UN research project into the effects of the recession on southern European countries. He even, some reports say, tried to pass himself off as a former adviser to Portugal's President, Joaio Sampaio, and the World Bank.

Blessed with such an impressive CV, Mr Baptista's subsequent criticisms of the Lisbon government's far-reaching austerity cuts, as well as dire warnings that the UN planned to take action against it, struck a deep chord with its financially beleaguered population.

According to the Spanish newspaper El País, his powerfully delivered comments at a debate at the International Club, a prestigious Lisbon cultural and social organisation last month, were greeted with thunderous applause and a part-standing ovation.

Then, in a double page interview in the weekly newspaper Expresso in mid-December, Mr Baptista da Silva continued to denounce the government's policies. That was followed by an interview for the radio station TSF, appearances in high-profile television debates and well-publicised meetings with trade union leaders to advise them on economic policies.

Yet in the country's jails, Mr Baptista da Silva's sudden appearance among the intellectual elite caused amazement among his former cellmates. A colleague from his old school, lawyer Ricardo Sa Fernandes, who had come across Mr Baptista da Silva behind bars by chance when visiting one of his clients, told Visao magazine that when he saw the convicted fraudster on TV he was "staggered by his ability to put his past life behind him".

Mr Baptista da Silva's comeuppance began when the UN confirmed to a Portuguese TV station last month that he did not work for the organisation, not even as a volunteer, as he later alleged. Further media investigations uncovered his prison record and fake university titles, though Mr Baptista da Silva's claims to have studied economics have not been categorically disproven.

After sending out a press release blasting his former journalist friends and colleagues for what he called a "witch-hunt", Mr Baptista da Silva has now disappeared completely from public life, and there are reports he is under investigation for fraud charges by the police.

Meanwhile, the media's search for an equally articulate and charismatic replacement critic of the government's economic policies – although perhaps not one with such overwhelmingly impressive academic credentials – continues apace.