Hundreds of art lovers examined the fake painting as they browsed the high-profile show of world-famous paintings by the likes of Pablo Picasso and Henri Matisse on loan from the Pompidou Centre in Paris.

Depicting a scene of the Hong Kong skyline shrouded in smog, the picture features a sailor with a speech bubble declaring "Donald We Can't Breathe", a reference to political leader Donald Tsang, who has been accused of doing too little to rectify the city's chronic pollution problems.

"It's a way of getting the message across that more needs to be done to clear up the air here," said activist Matt Pearce, who smuggled the canvas in and stuck it to a gallery wall using adhesive.

The protest was timed to coincide with Tsang's state-of-the-territory policy address Wednesday, in which environmentalists hope he will introduce new air-quality improving initiatives.

Pearce, well known in Hong Kong for pulling political eye-catching stunts, captured the prank on film, which he posted on the website YouTube.com.

"I want people to consider this as Donald Tsang gives his address," said Pearce.

Pollution has become a key political issue in Hong Kong as smog levels have risen to often dangerous levels. Poor air quality cut visibility to less than one kilometre (about half a mile) on more than 50 days last year.

While the problem is mostly due to factories across southern China's booming manufacturing centre in Guangdong province, local coal-burning power stations and diesel-powered buses are also major contributors.

The Hong Kong government recently launched an "Action Blue Sky" campaign to persuade citizens to cut down on air conditioner use and slash energy consumption.

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