Three years after the armed forces crushed their Tamil Tiger enemies, Sri Lanka's government is turning on former allies, with the head of the Supreme Court the latest to fall from grace.

Evoking memories of the demise of ex-army head Sarath Fonseka, who ended up behind bars after trying to run against President Mahinda Rajapakse in 2010, the ruling party has submitted a motion to impeach Chief Justice Shirani Bandaranayake, government and parliamentary officials announced Thursday.

The move comes weeks after senior journalist Frederica Jansz, a prosecution witness against Fonseka, was sacked as editor of the Sunday Leader newspaper. Jansz, who is now trying to get asylum abroad, says she was ousted for resisting demands by its new owner to temper criticism of Rajapakse and his family.

The government's opponents say no one should be surprised that the regime's former friends are now regarded as its enemies.

"The government is all out to suppress anyone who tries to stand up against the executive," opposition lawmaker Suresh Premachandran told AFP.

Bandaranayake, a 54-year-old former professor of law, had been hand-picked for the top judicial job by Rajapakse's government last year. Her husband was also appointed to politically sensitive posts in state financial institutions.

But the relationship is now in tatters, with Chandima Weerakkody, the deputy speaker of parliament, telling reporters Thursday that "government MPs have handed over a motion calling for the impeachment of the chief justice".

While Weerakkody did not give details of the motion, one of Rajapaske's ministers told a press conference there had been "disagreements" between the government and chief justice over a period of time.

"The government group believed that the judiciary is overstepping... its authority," said Information Minister Keheliya Rambukwella.

A sign that the chief justice's days were numbered came last week when Foreign Minister G. L. Peiris told MPs that Bandaranayake had "violated the constitution" by appointing a junior judge to head up a judicial watchdog.

The government's anti-graft panel has also filed a corruption complaint against Bandaranayake's husband, Pradeep Kariyawasam, who resigned recently as head of state-run Savings Bank after a controversial share purchase deal.

Analysts say the real reason behind the impeachment move is Bandaranayake's decision to shoot down a bill that sought to transfer powers from local bodies to the economic development ministry, headed by Rajapakse's younger brother Basil.

Victor Ivan, author of a book on the relationship between the Sri Lankan government and judiciary, said it was a classic case of friends turning foes after courts started asserting their authority in recent months.

"The judiciary and the executive behaved like very good buddies in the past," Ivan, a former journalist who describes himself as an "outspoken friend of the president", told AFP.

"Now that rulings are going against the government, they are fighting in public.

"It is like two freight trains moving at each other at high speed. Both will be destroyed as a result of this confrontation. It will also undermine public confidence in both institutions."

The push against the Supreme Court head has echoes of the fate of Fonseka, who became a national hero after crushing the Tamils in their northern stronghold in 2009 after a 37-year conflict.

Despite his hero status, Fonseka was hauled before the courts in 2010 on charges of "irregularities in military procurements" in what he argued was a ploy to torpedo his political ambitions.

He was swiftly jailed and stripped of his right to contest elections before being granted a presidential pardon in May this year.

The government's latest stand-off with the judiciary comes at a time when it faces heightened international scrutiny of its rights record amid allegations that up to 40,000 civilians were killed in the final months of fighting with Tamil rebels.

The United Nations Human Rights Council in Geneva starts its four-yearly review of Sri Lanka later Thursday.

"Sri Lanka has a difficult job defending its record in Geneva," said moderate Tamil politician and former lawmaker Dharmalingam Sithadthan.

"The clash with the judiciary will only make it more difficult for the government."