The Budget session of Parliament beginning on Monday portends a tough time for the government against the backdrop of reverses the Congress suffered at the Assembly elections and the possibility of issues like federalism bringing unlikely forces together.

The Congress heading the UPA may not be in a position to take even the allies for granted with a key coalition constituent Trinamool making it clear it was against a cut in fertiliser subsidy and rise in petroleum prices.

Trinamool supremo Mamata Banerjee has also joined non-Congress chief ministers in opposing the proposed National Counter Terrorism Centre(NCTC).

With Congress under pressure in the wake of its debacle in the Assembly polls, Opposition leaders have hinted that the session would see floor coordination between allies of Congress, its supporting parties and the opposition on the issue of federalism.

Prime Minister Manmohan Singh and UPA chairperson Sonia Gandhi face an unenviable task in the three-month long session which will commence with President Pratibha Patil's customary address to the joint sitting of the Lok Sabha and the Rajya Sabha. This will be Patil's last such address as she retires in July.

The Union Budget 2012-13 will be presented on March 16, four days after Parliament begins its Budget session.

While the Rail Budget will be presented on March 14, the Economic Survey outlining Government's assessment of the economy will be tabled on March 15.

The remarks of Trinamool Congress leader and Railway Minister Dinesh Trivedi on the possibility of mid-term polls are also expected to find its echo during the Budget session. Trivedi has since said his party has no intentions to rock the UPA boat.

The first part of the Budget session will conclude on March 30 and the second phase will start from April 24 after a three-week recess during which Parliamentary Standing Committees deliberate on proposals of different ministries.

The session is expected to conclude on May 22. The budget session, which generally starts in the third week of February, has been delayed this time due to the Assembly elections in five states, including Uttar Pradesh.

Ahead of the session, Congress has sought to reach out to allies by expressing readiness to walk the extra mile to strengthen coordination with them. It has also given hints that it was open to the idea of a UPA Coordination Committee.

Just after the assembly poll verdict, Congress president Sonia Gandhi has assured regular interaction with allies and expressed the hope that allies and the opposition will support the people-oriented measures.

The Congress refrain is that Budget cannot and should not be held hostage to political expediency as Budget and other attendant legislations are extremely critical for growth and progress of the nation.

BJP is claiming that the issue of federalism will be trumped up by allies of the Congress, outside supporters of the UPA coalition and the opposition parties.

"The issue of federalism has become a catalyst for a unique alliance among the allies of Congress, supporting parties and the opposition on the floor of the House", BJP spokesman Prakash Javadekar said.

The opposition are expected to raise several issues during the session including the "anti-farmer" move of banning cotton exports, he said.

Mamata Banerjee has reportedly complained that the Trinamool Congress was not being consulted on major policy issues. Her party wants a special package for West Bengal.

She is said to have indicated that the party would oppose any fresh moves to bring the pension bill, Lokayukta provision in Lokpal and allowing FDI in retail.

Opposition parties are gearing up to corner the government on a host of issues, including NCTC and Centre-state ties and target the UPA for alleged trampling of the principles of federalism.

They also plans to raise the controversial ISRO-Devas deal and the treatment meted out to former ISRO chief G. Madhavan Nair as also the Kudankulam nuclear power project issue.

An all-party meeting convened by Lok Sabha Speaker Meira Kumar last week had seen Opposition leaders raising a variety of issues including repeated 'attacks' by the Centre on the federal structure of the Constitution, demand for white paper on black money and violation of the Model Code by several Union ministers.

BJP leader and Leader of the Opposition in the Lok Sabha Sushma Swaraj complained about the short duration of the first phase of the Budget Session at a time when the Opposition has plans to raise several issues.

The party is also planning to give a Calling Attention notice for discussion on the issue of a NRI couple being separated from their two kids in Norway.

Parliamentary Affairs Minister Pawan Kumar Bansal has expressed government's readiness to discuss any issue the Opposition was keen on raising.