This article is more than 9 years old

This article is more than 9 years old

A former government minister linked to India's biggest corruption scam is to be questioned by government investigators tomorrow in the latest twist in the scandal gripping the nation.

Questioning by the Central Bureau of Investigation of Andimuthu Raja, the former telecoms minister dismissed for his role in allocating 2G mobile phone technology licenses nearly three years ago, is unlikely to bring relief to the beleaguered ruling United Progressive Alliance coalition, led by the Congress party.

Opposition parties have blocked parliament and brought tens of thousands of protesters on to the streets, sensing that the government, in the second year of a five-year term, has been seriously weakened by the scandals revealed in recent months.

The so-called 2G scam, which may have cost the exchequer up to £25bn, is one of half a dozen corruption allegations currently laid against senior government figures.

Now the leadership of prime minister Manmohan Singh, a 77-year-old economist with a reputation for financial competence, is being questioned.

Other scandals involving senior Congress party figures included the appropriation of flats meant for war widows by senior soldiers and bureaucrats in Mumbai and suspected wrongdoing concerning allocation of contracts for the Commonwealth Games, held in Delhi in October. Also dominating headlines are apparent efforts by a lobbyist working for business interests to influence ministerial appointments – revealed through leaked phone taps.

Scores of other scams, ranging from schemes to embezzle subsidies for the destitute to corruption in bodies licensing pilots who go on to work for domestic airlines, have also been revealed in recent weeks.

Though often unrelated to government figures – one scandal in Karnataka state allegedly involves politicians from the opposition Bharatiya Janata party – they have added to the perception that corruption has become rife in public life. Brahma Chellaney, a respected analyst and academic, wrote in The Hindu newspaper that though India confronts several pressing national security threats "only one of them – political corruption – poses an existential threat to the state".

Surging food prices are also a problem for the government, particularly with a series of state elections due from the late spring.

At demonstrations this week many participants, including women and children, wore onion garlands in protest after retail onion prices more than doubled in the past week to 80 rupees (£1.15) a kg. "This is the exhibition of public anger, the beginning of a large nationwide protest against corruption and inflation," BJP spokesman Prakash Javdekar told reporters.

Abhishek Manu Singhvi, a Congress spokesman, said the party had taken "path-breaking steps to combat misconduct and corruption".

The opposition has threatened to close the spring session of parliament if the government does not agree to a joint parliamentary inquiry, which has wide power to summon officials, into the 2G scam.

Deadlock in parliament has meant a range of key economic measures scheduled have been delayed, undermining the credibility of a government voted in with a powerful mandate to push through reform. The opposition is hoping to be able to sustain the political momentum with two months of countrywide protest.