José Luis Moyá's dedication to coaxing information from the Mexican authorities began two decades ago when, as a government employee, he made a fuss about the inflated price paid for equipment to instal a laser beam – which he claims never worked anyway – on top of the capital's Monument to the Revolution. "I lost my job, and that is how it started," he says.

At first, Moyá claims, he relied on information leaked to him from contacts he had established within different government bodies. He subsequently made those sources public through media contacts. Things really took off, however, after the enactment of freedom of information legislation in the wake of Mexico's transition away from one-party hegemony in 2000.

Moyá, 52, is one of the few people who really knows how to word requests in a way that forces revealing responses from bureaucrats instinctively accustomed to keeping information controlled. And nobody else has the energy to do it quite so often. Moyá claims to have made between 2,000 and 3,000 requests for information and appeals for the revision of unsatisfactory answers.

"They call me an anti-corruption terrorist," he says with pride.

While Moyá specialises in suspicious contracts, his concerns go beyond exposing politicians, bureaucrats and private companies getting rich at the expense of Mexican taxpayers. His claim to have proven the purchase of overpriced spying equipment is punctuated by a diatribe about the surveillance state; his allegation that the purchase of police patrol cars involved dirty dealing implies that, as a result, funds have been denied to projects that could help the country's security crisis.

"The problem is that the system covers up for corrupt politicians and nothing happens to them," he says. "But an ordinary citizen who steals food is vulnerable to extortion or being put in jail."

Moyá's style – working alone on a vast variety of different topics – is not common for Mexican campaigners, and he has been accused of having a mercenary attitude to transparency, allegedly accepting money from politicians to dig up information about rivals.

He concedes that, as well as supporting himself financially with income from rented properties, he is sometimes commissioned to search for information by politicians and functionaries "who don't dare do it themselves". He also says that having contacts in high places, and in the media, makes him feel relatively safe, despite instances of harassment.

But, Moyá insists, his motivation boils down to a need to expose corruption wherever he finds it and – while he revels in "small victories" here and there that lead to the cancellation of a programme, or the sacking of an official – he finds it in just as many places today as he did when he first started.

"The authorities have got more sophisticated in the way they pretend to be attacking corruption and in the way they claim that there is more transparency," he says. "But the truth is that impunity now is just as bad as it ever was."

Clear thinking

What does transparency mean to you?

It is a way of obliging governments to spend taxpayers' money in an honest way.

Why is access to information important in development?

If we know how the money is spent then it is more likely to be of benefit for society. Corruption is the biggest block to development.

What is the one piece of information you most want released?

The money controlled by the union of Pemex, the state-owned oil company. The union receives a lot of public money, but how it is used is completely opaque.