Britain and Canada raised concerns Thursday that expatriates living and working in Hong Kong could face extradition to mainland China under a controversial proposed extradition law, risking a chill on commerce.

Hong Kong's pro-Beijing authorities are pushing a bill through the legislature that would allow extraditions to any jurisdiction with which it doesn't already have a treaty - including mainland China.

Historically, the semi-autonomous city has balked at mainland extraditions because of the opacity of China's criminal justice system and its liberal use of the death penalty.

"We are concerned about the potential effect of these proposals on the large number of Canadian and UK citizens in Hong Kong, on business confidence and on Hong Kong's international reputation," Britain and Canada said in a joint statement.

"Furthermore, we believe that there is a risk that the proposals could impact negatively on the rights and freedoms set down in the Sino-British Joint Declaration. 

"It is vital that extradition arrangements in Hong Kong are in line with 'one country, two systems' and fully respect Hong Kong's high degree of autonomy."