The self-styled adviser to former defence secretary Liam Fox will not face criminal charges, prosecutors announced.
Adam Werritty was under investigation after describing himself as Mr Fox's adviser on business cards and allegedly accepting donations as part of that role.
The new group is intended to unite grassroots Tory activists and more senior politicians who;
As well as Mr Davis and Dr Fox, other MPs named as backers are Conor Burns, Robert Halfon, Priti Patel and Dominic Raab.
Two Tory big beasts are launching a group campaigning for "radical" policies, amid pressure on David Cameron's leadership.
David Davis and Liam Fox will unveil Conservative Voice, urging the party to show "serious ambition".
Although organisers insist the group will work alongside the leadership, the move comes with the Prime Minister struggling to placate Conservative traditionalists from two former front-benchers who ran against him for the party leadership.
Labour leader Ed Miliband has accused David Cameron of having no clear position on whether there should be a referendum on Britain's membership of the EU.
Labour leader Ed Miliband has mocked David Cameron's stance on an EU referendum.
He told MPs that the Prime Minister was trying to appease the divisions in his own party, rather than acting in the interests of the nation.
Mr Miliband accused the PM of having a "hokey cokey weekend".
David Cameron has risked angering Tory backbenchers by again refusing to back a quick poll on Britain's membership of the European Union.
The PM said he did not believe that voting to leave the EU would be the best thing for the country.
Former defence secretary Liam Fox said if there were further treaty changes, a referendum on Europe would be inevitable.
He said he favoured cuts to public spending to fund tax cuts.
Speaking to Dermot Murnaghan on Sky News, Dr Fox said: "Clearly, if there were further changes that would have to be put to a referendum in Britain.
"But the whole eurozone problem was entirely predictable. They wouldn't decide whether it was a political project or an economic project. They are still not doing so.
"It now looks very wise from (former prime minister) John Major at the outset to say 'who would go into anything that didn't have an exit'.
"How right he was to disregard the advice of the Labour Party at the time and keep us out of the single currency."