NEW DELHI (AFP) - A former Indian army chief who resigned from the military following a controversy over his age on Saturday announced he had joined the Hindu nationalist opposition ahead of looming elections.

India's massive armed forces normally stay out of politics, but retired General V.K. Singh had been tipped to enter the arena since resigning as the head of the army in May 2012 after being accused of fudging his birth date to extend his service term.

Singh said he was joining the Bharatiya Janata Party (BJP) - tipped to sweep the polls due by May - to "elect a stable, powerful government that can take decisions in the national interest".

The ex-army chief had been expected to become a BJP member after appearing last year at a rally with the opposition party's prime ministerial candidate, Narendra Modi, where they addressed retired soldiers.

BJP backers are hoping Singh's support will bring votes from India's million-strong defence forces, an important constituency.

Several other former defence officers joined the BJP with Singh, who sought to rally the crowd with cries of "Jai Jawan, Jai Kisan" - "hail soldier, hail farmer".

Singh's relations with the scandal-tainted Congress government, which is struggling in opinion polls, were soured by the row over his birth date.

In an unprecedented move by a serving army chief, Singh dragged the government to the Supreme Court in a bid to prolong his tenure by nearly a year.

The trouble sprang from two sets of birth records held by the army for the former general.

The court sided with the government in its view that the birth date, which made Singh older, should prevail.

After retiring from his post, Singh blamed the government for a host of problems during his two years as army chief including rows over dilapidated weaponry.

In his address at the BJP's headquarters in New Delhi on Saturday, Singh accused the government of failing to ensure the security of India's armed forces.

He noted incursions in recent months by Chinese forces along India's porous border as well as deadly guerrilla raids by Pakistan-based militants on Indian soil.