The chief executive of the world's biggest arts event has made a robust defence of both its ethos and its economics on the eve of its 2013 launch.

Kath Mainland, who runs the Festival Fringe Society which organises the annual event, has responded to claims Edinburgh's Festival Fringe is operating a bubble or broken economy.

She said the heart of the Fringe was its open access to anyone who can put on a show.

Ms Mainland said issues around the expense and risk of staging a show at the Fringe have been the same for a long time, especially relating to accommodation costs, venue use and marketing.

However, she disputed any suggestion the Fringe, which recorded 1.8 million tickets issued last year, was now a harder environment than in any other year.

Last year comedian Stewart Lee said the Fringe had entered a state that "reflects the cultural bankruptcy of late capitalism".

This year, producer and director Pippa Bailey said: "As a microcosm of wider society, the fringe system mirrors an unstable economy, a sub-prime market waiting to implode with artists prepared to spend beyond their means and operate at a loss while hope and desperation drive this bubble economy."

The Fringe Society, Ms ­Mainland said, has frozen registration fees since 2008, and provides a list of affordable accommodation to companies and performers. This year the society is also reducing its commission on ticket sales, from 6% to 4%, so more goes to venues.

It has been estimated the Fringe annually generates £142m for Edinburgh and the Scottish economy.

The programme has grown again this year, with a 6.5% rise in shows this year compared to the previous one. There will be 2871 shows, performed by 24,107 artists in 273 venues.

Previews have already begun in the 'week zero' of the Fringe, which officially starts tomorrow.

Ms Mainland said: "If you say it is worse or more difficult, what is that based on? Maybe if there was documented evidence of it being more difficult than before, but that is not there at the moment. I think the difficult of putting on shows is a perennial story.

"We could do an expensive piece of research [into the issues] but I am not sure how useful that could be, there are so many variables at the Fringe and so many ways of doing it, I think it would only be a distraction. Instead we concentrate on ways we can help."

She said putting a show on was always a risk but this could be mitigated if you know "what you are getting yourself into" and the help the Fringe Society offers.

Ms Mainland said criticism of specific venues being more prominent than others, such as Underbelly, the Pleasance and Assembly, should be tempered by the risks they also were taking.

She said: "The venues are not in it for the money, these are very expensive enterprises, and they are cultural entrepreneurs. The essence of the Fringe, I will say it again, is that it is open access and anyone can take part in it. You cannot go messing with that.

"There is a quite a bit of co-operation already but I agree with Bill [Burdett-Coutts, director of Assembly] and think there can be co-operation and competition at the same time. I think people like Bill, of course they want to do well, but they want the Fringe as a whole to do well."

Tomorrow the Fringe begins with a speech from theatre director Mark Ravenhill in the festival's first inaugural address at Fringe Central, based at Edinburgh University's Appleton Tower. In the programme, theatre shows have increased this year from 751 shows to 824.

For the first time in years, the percentage of shows classed as comedy has fallen from 36% to 33%, with a corresponding growth in spoken word and cabaret shows. One of the biggest venues in Edinburgh, the McEwan Hall, is also back after a two-year gap.