(Bloomberg) —Brexit negotiators reconvening in Brussels should focus on the economy on both sides, the British Chambers of Commerce and the Association of German Chambers of Commerce said.

The two lobby groups on Monday called for clarity and certainty as the latest round of divorce negotiations begins. Critical areas that are yet to be resolved include worker’s rights, customs arrangements and tax procedures, the chambers said.

There is great uncertainty in the business community all across Europe, they said in a joint statement on Monday. A survey by the German group has found out that the business outlook of companies that are engaged in trade with the United Kingdom is worsening, due to the expectation of cost burdens from limits on free movement of workers, taxes, tariffs and increasing bureaucratic hurdles at Europe’s new borders negatively affecting business on both sides.

Work must begin on transitional arrangements, to give firms confidence to make investment decisions, Adam Marshall, the BCC director general, said in the statement.