The collector Charles Saatchi is to go into direct competition with the Tate by opening what he believes is the world’s biggest private gallery of contemporary art. With 15 large rooms spread over three floors and covering 50,000 sq ft, the new Saatchi gallery in Chelsea, west London, will begin with a show of contemporary Chinese art bought by the former advertising executive over the past three years.

Like Tate Modern, the Saatchi will be free to visitors when it opens in late spring. His previous gallery at County Hall, London, charged £8.50 and closed in 2005.

There are numerous private collectors of contemporary art, but few anywhere near the scale of Saatchi show such works to the public.

Saatchi, who will use the new venue for a rotating series of temporary exhibitions from his personal collection, said: “Free entry can only help spread the interest in contemporary art.”

The collector, who came to public prominence as the patron of former Young British Artists such as Damien Hirst, has had a troubled relationship with the Tate. He once claimed its director, Sir Nicholas Serota, had turned down an offer to give the Tate a large part of his collection. Serota has denied this.

Unlike its south London competitor, which covers modern art since 1900, Saatchi’s new gallery will concentrate purely on the work of today.

Saatchi, 64, acknowledges he is taking a risk by starting with a show of nearly 100 works by 30 contemporary Chinese artists – since few members of the public would be able to name a single modern artist from the country.

However, he is confident the large, brightly coloured works will suit the whitewalled rooms and attract visitors to shows at the former Duke of York’s barracks, off the King’s Road.

Chinese contemporary art has flourished over the past five years and has been attracting buyers who have paid, at times, more than £1m for a single work. The Chinese style previously aped that of Andy Warhol and pop artists and so felt comfortable to western eyes. Saatchi himself has paid nearly £1m for a handful of works from Chinese artists such as Zhang Xiaogang and Zeng Fanzhi.

“I think there are now quite a number of Chinese artists as good as any in the West,” Saatchi said. “We were initially sniffy, as it seemed derivative, but we’ve been won over.”

He has already bought several works from Phillips de Pury, the New York-based auction firm whose sponsorship ensures the gallery’s free admission policy. Later shows will also be sponsored by the firm, which is opening a new British and European headquarters and auction rooms in Victoria, central London, at the end of this month. In return, Saatchi has an arrangement to conduct most of his buying and selling through Phillips, whose spokesman said: “There is an understanding he does business with us.”

Saatchi hopes to attract 1m visitors a year, compared with the 600,000 in three years who came while his gallery was housed in the County Hall building, on the Thames opposite Big Ben. Tate Modern has about 4m visitors a year.

He has also decided the gallery will open from 10am to 10pm every day except Sundays, when it will close at 8pm. This will mean it will have longer opening hours than any other British gallery or museum.

Saatchi launched the careers of many British artists, including Hirst and Tracey Emin, from his original gallery in St John’s Wood, north London. In early 2003, he moved from there to County Hall, but had a difficult relationship with his landlord, culminating in the closure of the gallery. Many visitors – including most critics – found the small, wood-panelled rooms unsuited to contemporary art.

Tate Modern, which opened in 2000 less than a mile away on the south bank of the Thames, overshadowed Saatchi’s efforts with a combination of its modern collection and the successful installations in its turbine hall.

Saatchi has sold nearly all the British art he collected in the 1990s. The sole work by a British artist to be permanently on display in his new gallery is Richard Wil-son’s 20:50, an installation of oil in steel pools, shown earlier at County Hall.

After the Chinese show, the gallery will put on exhibitions by new US artists and then a show of contemporary Indian art.

Hey, big collector

Other noted collectors of contemporary art include:

- Frank Cohen, former owner of a chain of DIY shops. Manchester-based, he has more than 1,500 works and a gallery in Wolverhampton.

- David Roberts, the property developer son of a Glasgow shipyard worker. He has 2,000 works, including pieces by Damien Hirst. He owns Gallery one one one in London.

- Young artists have been promoted by Anita Zabludowicz, a Newcastle-born collector. She has a gallery in London.

- Sir Elton John plans to house his collection in a gallery at his Berkshire home but has yet to win planning permission.

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