Nairobi - Kenya's biggest donors on Thursday issued a fierce rebuke of rampant corruption in the east African nation, warning it weakened economic growth and security and threatening to impose travel bans.In a rare joint show of force, a dozen ambassadors from key donor nations - including the United States, Britain, the European Union, France, Germany and Japan - together visited Kenya's Ethics and Anti-Corruption Commission (EAAC) for talks."Corruption is undermining Kenya's future," said US ambassador Bob Godec, reading a joint statement by senior foreign diplomats, including from Canada, Finland, the Netherlands, Norway, Sweden and Switzerland."We share the concern of Kenyans at the ongoing problem of corruption," Godec said, warning that "corruption threatens the country's economic growth, the provision of government services, and security. It deters investment and costs jobs."Tough and swift actionKenya, which is placed near the bottom of Transparency International's annual corruption index, coming in 145th out of 174, has long been blighted by graft.Newspaper front pages this month have been dominated by a string of graft allegations.They include a parliamentary inquiry into the devolution ministry, where officials are alleged to have massively inflated government purchases, including claiming to have bought simple pens for $85 each.It follows another widely publicised case in September, when protesters in the western Bungoma district marched on government offices after officials bought 10 wheelbarrows costing over $1 000 each.Godec said Kenya was facing a "crisis" of corruption."All allegations of corruption must be investigated. When evidence of corruption is found, those responsible must be prosecuted and, if guilty, appropriately punished - regardless of position or wealth," he said.The diplomats said they were "committed to taking tough and swift action" when their own citizens are involved, and to trace ill-gotten gains in their own countries.They also threatened, "to impose travel restriction on those responsible for graft".