NEW DELHI, Sept 18 (Reuters) - Prime Minister Narendra Modi and lawmakers paid tribute on Monday to India's parliament on the eve of its shift from a British colonial-era building to a brand new complex.

Built by British architects Edwin Lutyens and Herbert Baker two decades before India's 1947 independence, the old parliament witnessed the tortuous birth of the republic and thereafter served as a custodian of the world's biggest democracy.

Now it is to become a museum, its 788 members moving to a new, triangular-shaped complex as part of a $2.4 billion rebuild of institutions with a more Indian identity.

"Today is an occasion to recollect and reminisce the parliamentary journey of 75 years of India before the proceedings are shifted to the newly inaugurated building," Modi told a special session before Tuesday's move.

In May, Modi inaugurated the new parliament, part of an ambitious redevelopment of the Central Vista complex in New Delhi, amid protests from opposition parties who had wanted India's president to inaugurate instead.

The new, larger four-storey building can seat 1,272.

"It is a very emotional moment to bid farewell to the old parliament building ... Its glory also belongs to us," Modi told lawmakers in the lower house of the old parliament.

His speech marked the start of a five-day special session called by the government, but there was no immediate confirmation on bills up for discussion.

Indian lawmakers usually meet thrice a year: a budget session, a monsoon session and a winter session.

While opposition leaders questioned the significance of the special session, they bid farewell to the old building and looked forward to better logistics, security and technology.