British government bond yields climbed to fresh 18-year highs on Wednesday as a global selloff in sovereign debt intensified amid growing concerns over inflation and rising oil prices linked to the escalating Iran war.The yield on the benchmark 10-year gilt rose to its highest level since June 2008 and was up 4 basis points at 5.268% shortly after 0700 GMT. The move came as investors reassessed the outlook for inflation and interest rates across major economies.According to Reuters, the latest rise in UK borrowing costs forms part of a broader global bond market selloff, with higher energy prices increasing concerns that inflation could remain elevated for longer. Rising yields are also raising questions about the ability of governments to manage increasingly expensive debt burdens.Read more: US Stock Market: Higher long-term Treasury yields face structural headwindsThe surge in gilt yields is particularly significant for Britain, where higher borrowing costs could increase debt-servicing expenses and put additional pressure on public finances. The UK already faces elevated debt levels, making the government's fiscal position more sensitive to movements in bond yields.The market pressure comes at a challenging time for Prime Minister Andy Burnham and Finance Minister John Healey, who are preparing for their first budget next month. Higher borrowing costs could reduce the government's room for manoeuvre and complicate efforts to balance spending priorities with fiscal discipline.Longer-term UK borrowing costs have also come under pressure. Reuters reported that the global bond selloff has been driven by a combination of inflation concerns, higher oil prices and growing worries over government debt sustainability.The rise in yields could also influence expectations for monetary policy. Persistent energy-price pressures could make it more difficult for central banks to ease interest rates, while investors are increasingly demanding higher returns to hold longer-dated government debt.For the UK government, the combination of elevated gilt yields, inflation risks and higher debt-servicing costs presents a difficult backdrop ahead of the budget. The latest market moves underline the growing importance of fiscal credibility as policymakers prepare their spending and taxation plans.(Disclaimer: Recommendations, suggestions, views, and opinions given by experts are their own. These do not represent the views of The Economic Times.)