The legislation is highly controversial and there are widespread fears in Hong Kong that it will harm civil liberties.
But the government on Thursday brushed aside the suggestion that foreign banks might relocate.
The proposed legislation would outlaw acts of treason or subversion against China.
Banker and local legislator David Li earlier said the financial community was fearful the laws would restrict the free flow of information in the territory.
"They're concerned about freedom of information. They're concerned that by [restricting] it, there may self-censorship of the press," said Mr Li, who is chairman of the Bank of Asia and who also speaks for the financial sector in Hong Kong's legislature.
"They're concerned that Hong Kong will not be what it has always been. But they want to know for certain, because some of them are even considering increasing their presence elsewhere rather than Hong Kong."
The issue of new national security laws is the most contentious Hong Kong has faced since it was returned to China.
The government unveiled its proposal a few weeks ago and since then there has been an outpouring of opposition to the legislation.
Our correspondent in Hong Kong, Damian Grammaticas, says Mr Li's warning is a stark one, coming as it does from the firms that have helped make Hong Kong wealthy.
Many fear Hong Kong is pressing ahead with the laws to satisfy Beijing's desire for greater control over the territory
The bankers are also thought to be concerned about their future freedom to do business with clients in Taiwan, or to handle sensitive economic information from Chinese state firms or banks - information which Chinese law could classify as state secrets.
They have said they would like to see the full wording of the laws, but Hong Kong's Government is refusing to publish the draft legislation.
It will only be seen when it is submitted to the legislature, a rubber-stamp chamber that is unlikely to make many changes.
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