The Democratic Alliance is proposing legislation to outlaw public officials from doing business with the state, party leader Helen Zille said on Friday.

Zille wrote in her weekly newsletter that the party was going to launch a national campaign demanding financial disclosure forms for all elected representatives and officials.

"Public servants must not be able to do business with the state. That is an invitation to corruption," Zille said.

"The DA is proposing legislation to outlaw any officials from awarding government contracts to private companies in which they have interests."

Loopholes in the law mean that a "clean and principled public service" can never exist on its own, Zille said.

"For example, information on spouses is confidential, so officials could set up companies in their spouse's name and give government contracts to them.

"It is difficult to counter such corruption."

It is important to foster high ethical standards, she said.

"Elected officials in South Africa are very well paid compared with the populace at large, which makes resorting to corruption even more disgraceful."

She said the Nelson Mandela Bay Metro, where a R3 million road tarring contract was awarded to a company whose director was a councillor at the metro, was one example where compliance with financial disclosure was unsatisfactory.

"The DA wants there to be no doubt whatsoever that all officials are obliged to make full financial disclosure and we want there to be no room for prevarication or evasion.

"We want the financial disclosure forms to be standardised into one form that will be used all over the country, in national, provincial and local legislatures. This will eliminate the uncertainty that pertains now.

"We also want to define very clearly what is confidential and what is public information. There must be no chance to hide public information behind the confidential.