After finishing school at Aabenraa Statsskole, Bonde studied political science at Aarhus University. He was politically active at a young age as member of the Radikale Venstre, a centrist party. From 1966, he was the party's Aarhus-candidate for Danish Parliament, but resigned his candidateship before the 1971 elections. In 1971-1972, he was chairman of the party's youth wing.
In connection with the Danish referendum on EC membership in 1972, he cofounded Folkebevægelsen mod EF (People's Movement Against the EC). Starting the same year, he worked as a journalist on the weekly/biweekly newspaper NOTAT, which began as part of the campaign surrounding the referendum and became one of the main organs for Danish EC-sceptics. The newspaper was reorganised as Det ny Notat in 1974, with Bonde as cofounder and editor until 1979.

For the first direct elections to the European Parliament in 1979, Bonde was elected, representing Folkebevægelsen mod EF. Serving on the budget committee, he made a name for himself pushing for transparency and greater parliamentary control in spending.
After reelection in 1984, he helped organise the Rainbow Group, an alliance of small, independent green, leftist and regionalist parties in Parliament that did not belong to any of the larger coalitions. The Rainbow Group was active 1984-1989.

In connection with the Danish referendum on the Maastricht Treaty in June 1992, Bonde cofounded Danmark 92, an organisation advocating a no to the treaty. After the referendum, in which accession to the treaty did not pass and therefore resulted in a wider political discussion on lack of democracy in the EC, Bonde cofounded Junibevægelsen (The June Movement, so named because the referendum took place in June), a Danish political organisation of EU sceptics. From 1993 he represented Junibevægelsen in parliament, rather than Folkebevægelsen mod EF, and continued to do so until his retirement.

During his almost 30 years in Parliament, he was member of a wide selection of committees and groups, among others:
He was member of the Bureau of the Group for the Technical Coordination and Defense of Independent Groups and Members, member of the Rainbow Group, member of the Federation of the Green-Alternative European Links, member of the Agelev-Ecolo, member of the European Free Alliance in the European Parliament, Deputy-Chair of the Europe of Nations Group (Coordination Group), Deputy-Chair and Chair of the Group of Independents for a Europe of Nations, Co-Chair and Chair of the Group for a Europe of Democracies and Diversities, Co-Chair and Chair of the Independence/Democracy Group.

He was Chair of the Delegation for relations with Iceland, Vice-Chair of the Delegation for relations with Norway, Vice-Chair of the Delegation for relations with Switzerland, Iceland and Norway and Vice-Chair of the Delegation for relations with Switzerland, Iceland and Norway and to the European Economic Area (EEA) Joint Parliamentary Committee.

He was also a member of the Committee on Budgets, member of the Committee on Transports and Tourism, member of the Committee on Energy, Research and Technology, member of the Delegation for relations with Iceland, member of the Committee on Economic and Monetary Affairs and Industrial Policy, member of the Delegation to the EC-European Economic Area Joint Parliamentary Committee, member of the Subcommittee on Human Rights, member of the Committee on Institutional Affairs, member of the Committee on Foreign Affairs, Security and Defence Policy, member of the Delegation to the EU-Malta Joint Parliamentary Committee, member of the Conference of Presidents, member of the Committee on Constitutional Affairs, member of the Delegation for relations with Switzerland, Iceland and Norway, member of the Delegation for relations with Switzerland, Iceland and Norway and to the European Economic Area (EEA) Joint Parliamentary Committee.

Bonde resigned his seat in the European Parliament in May 2008.