* UK limits workers with no job offer to 1,000 a year
* Workers with skilled job offers boosted to 20,700 a year
* No cap on senior staff transferred by firms from overseas
(Adds comment and details)
By Matt Falloon
LONDON, Nov 23 (Reuters) - Britain will cut the number of workers it allows in from outside the European Union by a fifth, introducing a cap as part of efforts to slash immigration levels by 2015, the government said on Tuesday.
But the Conservative-Liberal Democrat coalition, in power since May, said there would be no cap on staff earning more than 40,000 pounds ($63,500) a year who were transferred to Britain from a company post elsewhere.
Business lobby groups, opposition politicians and some Lib Dems have warned the government that limiting migration flows into Britain will take its toll on the economy, holding back productivity and potentially driving up wage costs.
However, social tensions over high levels of immigration played a crucial role in this year's election campaign and all main political parties made pledges to take a tougher stance.
Unemployment in Britain is running at 7.7 percent and ic spending cuts mean that almost half a million public sector workers risk losing their jobs.
Conservative interior minister Theresa May said the government wanted to bring net migration -- immigration minus emigration -- down from almost 200,000 to tens of thousands by 2015, when the next parliamentary election is due.
"We must tighten up our immigration system," May told parliament. "It is possible to reduce numbers while promoting growth and underlining the message that Britain is open for business."
CAP FROM 2011
The number of workers entering Britain from outside the EU will be capped at 21,700 a year, compared with around 28,000 in 2009. The measures will take effect from April 2011. As part of the European Union, Britain has an "open door" policy for economic migrants from most of the 27-nation bloc.
Those allowed to enter without a job offer will be slashed by 13,000 from last year's level to 1,000 and permits will be limited to "exceptional talent" such as scientists, academics and artists.
The number of workers with job offers allowed in will be increased by nearly 7,000 to 20,700, although permits will be restricted to graduate-level jobs, May said. There will be no limit on investors and entrepreneurs.
May also said she would stop temporary workers coming to Britain and settling permanently.
"We will end the link between temporary and permanent migration," she said.
Business groups welcomed the decision not to limit company transfers for those earning more than 40,000 pounds a year but warned the government that a cap on non-EU skilled workers could mean that Britain would lose out on attracting talent.
"We are still concerned that the lack of flexibility inherent in a cap will have a detrimental effect on London's competitiveness and productivity," said London Chamber of Commerce and Industry chief executive Colin Stanbridge. (Editing by Keith Weir and Kevin Liffey)