Setting aside ideological differences, the Congress, the Bharatiya Janata Party and the Communist Party of India � Marxist have joined hands in Sikkim to unitedly fight Chief Minister Pawan Kumar Chamling's Sikkim Democratic Front in the assembly polls scheduled to be held later this year.

The alliance between the three national level parties and two other regional parties -- Sikkim Himali Rajya Parishad Party and Sikkim Gorkha Prajatantrik Party -- has been named the United Democratic Front, senior Congress leader and former minister K N Upreti, the Front's chief coordinator, told reporters in Gangtok on Sunday night.

The assembly polls would see a direct contest between the SDF and UDF in all the 32 seats in the state, he said.

The decision to form the UDF was taken in a meeting of Opposition leaders including former chief minister and Sikkim Pradesh Congress Committee president Nar Bahadur Bhandari, BJP state unit president Hare Ram Pradhan, SHRPP president A D Subba, SGPP leader N B Khatiwada and CPI-M state committee member Anjan Upadhyaya, Upreti said.

Appealing to voters to elect the UDF, he alleged that during the last 15 years of its rule, the SDF had trampled upon the people's fundamental rights.

Calling for parivartan (Change), Upreti asked other opposition parties too to join the UDF banner to prevent division of votes against the ruling party.

"UDF's doors are open to all like-minded parties," he said.