By Torin Douglas BBC media correspondent

So it's back to basics for Channel 4.

The channel, set up in 1982 as an alternative TV service serving minorities, has expanded rapidly over the last five years.

Under its previous chief executive Michael Jackson it spent millions of pounds on hundreds of extra staff, two new digital TV channels, hours of expensive American imports like Friends and The Simpsons and a costly expansion into the film distribution business, trying to take on Hollywood at its own game.

Now that process is to be thrown into reverse, as the new chief executive Mark Thompson - like Mr Jackson, a former head of BBC Television - reinvents the station, in the face of growing competition from bigger television rivals.

Mark Thompson is planning big changes at Channel 4

Changes in media ownership rules mean there could soon be a single ITV company, owned by an American giant like Disney, while BSkyB - controlled by Rupert Murdoch - could form a tie-up with Channel 5.

Many fear that in a more competitive commercial climate, Channel 4 - funded mainly by advertising - will become increasingly vulnerable.

It has just recorded a �20 million loss - its first in ten years - and there has been criticism of its heavy spending.

Radical overhaul

The advertising group Zenith accused it of extravagance, particularly during a sustained economic downturn.

The charge was rejected by Channel 4 - and its new boss - only ten weeks ago.

But now Mr Thompson is planning a radical overhaul of its programme schedules and structure.

"If we don't change the schedules, the way we work, the structure and scale of the organisation very radically indeed, we are not going to succeed," he told staff.

"We're entering a new environment, a much tougher one for the the channel competitively and financially.

"Just as when Channel 4 started, we have less money than most of our key rivals so we have to think harder. We have to box clever."

He pulled no punches on people's job prospects.

"It's going to be an exciting and positive time at the channel, but it's also going to be a bumpy time. Creating a leaner, less hierarchical Channel 4 will mean employing fewer people."

Will there be room in the new schedule for Richard and Judy?

The FilmFour production and distribution company is to be closed down and film-making brought back into the TV operation's programme department, under a new head of film.

Next year it will spend �10 million on film production, a third of last year's figure.

But the FilmFour digital TV channel - which is run separately - will stay on the air.

Mr Thompson is cutting the number of TV commissioning departments from 13 to eight, and integrating the programme team for the E4 digital channel into the main Channel 4 comedy and entertainment department.

Risk-taking spirit

Overall the Channel 4 staff - currently numbering 1100 - is likely to be cut to nearer the 650 it employed five years ago before the dash for growth.

There was more than a hint from Mr Thompson that he felt the channel had lost its way, and foresaken its roots, under his predecessor.

"That subversive, bold risk-taking spirit is there to be re-awakened and could be stronger than ever. It's a spirit you can only really foster when you're small and fleet of foot," he said.

Thompson said next year would be a year of transition, but the following year would be different.

"We're building from scratch, as if we were scheduling a new channel for the first time. We want a schedule with more risk and more confidence."

That could mean curtains for Channel 4 ratings stalwarts like Brookside, Countdown and Fifteen-to-One and the more recent and less successful import, Richard and Judy.