Northern line commuters are bracing themselves for nearly two years of travel misery after a the firm responsible for upgrading the line announced series of paralysing closures to carry out an engineering upgrade.

Tube Lines (TL) told City Hall earlier this month it was almost doubling requests for weekend closures (from 46 to 82) on the Tube’s busiest line, and that it wants to close stations early on weeknights.

Under current plans the line will close north of Kennington from 10pm for 16 months from July and during most weekends for 20 months starting in March.

More than 800,000 people using the “misery line” daily, and while other Tube lines will have to cope with additional passengers, commuters will have to line-up for replacement bus services home.

Richard Tracey, London Assembly member for Wandsworth, said commuters should now be consulted on when that should happen and floated the idea of shutting down the line for a whole month.

He said: “We now want the company to consult Tube users on what they think. For example it might be easier to shut the Tube for a whole month, say in August, than having a series of closures.”

He added: “It has been clear for sometime there would be some problems on the Northern line. Tube Lines was supposed to finish the Jubillee line extension in 2009 but that looks like it will now be finished in 2010. So we need to make sure the Northern line upgrade is on time.”

Tooting MP Sadiq Khan, who is also a transport Minister, said he favoured staggering closures and ensuring there was enough transport capacity on the buses to take the slack.

He said: “If you shut the line for a long period the local economy, retail and food, would suffer. You have 5,500 people working at St George’s Hospital and they do shift work at all hours, you also have a lot of cleaners so it would have a real impact on those workers.”

TL, which is also responsible for upgrading the Jubilee, Piccadilly lines, can ask for the closures under its PPP (Public Private Partnership) contract.

PPP has been slammed after Metronet, the other company to be awarded a major upgrade contract, collapsed in 2007, with an estimated cost to the taxpayer of £2billion.

Mayor of London, Boris Johnson, said the closures were “intolerable” and has asked TL to explain why the lengthy closures are necessary.