Square mile group TheCityUK has released its Budget wish list, urging the Government to improve tax competitiveness, boost regional growth and ensure EU market access when it reveals its economic priorities next month.
The organisation, which works on behalf of London's financial and professional services industry, says its proposals are geared towards "minimising uncertainty" and supporting the economy through the Brexit process.
The Chancellor's spring Budget will be revealed on March 8, and is expected to precede the Government's formal trigger of Article 50 due next month.
TheCityUK's budget submission revives calls for a bespoke deal with the EU that provides similar levels of access to the EU's single market as those current in place for financial and professional services.
Access is currently gained through passporting rights that allow financial services to trade freely across the union without needing to apply for permission in each member state.
Passporting rights are expected to be scrapped as Theresa May's government pursues a hard Brexit deal.
TheCityUK is pushing for a deal would be based on "mutual recognition and regulatory cooperation", which it says is in the "best interests" of both Britain and the bloc.
Chief executive Miles Celic said: "The UK is home to the world's leading international financial centre, powered by an industry which employs 2.2 million people, two thirds of whom are based outside of London in significant centres such as Edinburgh, Birmingham and Cardiff. It is integral to the UK economy, paying almost £72 billion in tax.
"Getting the right Brexit deal for the UK, the EU 27 and global stability - one that is orderly and provides as much certainty as possible - is fundamental to ensuring that the UK remains an attractive and internationally competitive place to do business, and so is ensuring the right policy environment to enable it to prosper."
The lobby group is urging the Government to do more to support the development of start up and and "innovation-focused" finance beyond London and the South-East of England, by setting up initiatives like a dedicated regional fund within the British Business Bank.
The government-owned bank does not invest directly in small firms but works with venture capital funds and funding platforms to finance small businesses.
TheCityUK is also proposing that the Government establish an office for tax simplification to help streamline and increase the competitiveness of Britain's tax system, but cautioned against the introduction of "sensitive new tax changes".
Mr Celic said: "Enhancing the clarity and competitiveness of the UK's tax regime, bolstering national productivity and supporting innovation across the country should be key priority areas."