The first conference guests to use the new Arena and Convention Centre Liverpool in 2008 will be forced to use temporary rooms due to delays with fit-out.
Events including the Liberal Democrat Spring Conference in March will be held in the temporary structures, which will be built on the arena floor at a cost of £500,000.
Liverpool City Council, operator of the ACC, has asked the North West Development Agency for funding to help meet the contingency costs.
One event in the 10,000-seat arena has been moved to another date due to a booking clash with the 1,800-seat convention centre next door, which will not be finished until later in the spring.
Around half a dozen conferences will be affected but there have been no cancellations. The ACC installed the same temporary rooms in a London warehouse and invited customers who had booked the centre to sample the arrangements. All were said to be content with the arrangement and pledged to continue with their bookings. It is not known what if any compensation will be paid out.
The delays, and a £9m cost overrun, are being blamed on a host of factors, from improvements to the specification for the convention centre, to supply problems with materials from China and Italy, and the wet weather in the summer.
A council spokesman said the extra costs would be met by a combination of English Partnerships, the NWDA and the council.
It marks the second increase in the budget after another £9m over-run was announced in late 2006. The total budget has risen from £146m to £164m, a 12% increase; marginal in comparison to such major capital projects as the new Wembley stadium or Millennium Dome.
The spokesman added that bookings for the convention centre for 2008 were well ahead of target and receipts to the council would make up for any up-front losses.
The first events in the ACC are the in-house party for Capital of Culture volunteers and ambassadors on 4 January in the arena, followed by children's stage show CBeebies on 6 January and the official launch concerts on 11 and 12 of January.
The first conferences do not take place until February and the temporary rooms are likely to be in use for around six weeks.
Seven hundred construction workers, led by main contractor Bovis Lend Lease, are now working round-the-clock shifts seven days a week to finish the building, designed by Wilkinson Eyre.