WASHINGTON (AP) _ Sen. Bob Dole's ties to an independent Kansas oil company run by political friends and contributors to his Republican presidential campaign are being questioned in a published report.

In 1989, Dole questioned the reliability of a Senate committee's investigation of Koch Industries, Inc., in an alleged oil siphoning scheme, Business Week reported.

The April 1 issue of the magazine also noted that last year, Dole proposed regulatory reforms that could help the Wichita-based company defend itself against a $55 million Justice Department oil spill lawsuit.

Dole's press secretary, C. Clarkson Hine Jr., told Business Week that Dole: ``simply joined three other senators, on a bipartisan basis, in expressing appropriate and legitimate concerns in an effort to ensure fair treatment by a Senate committee of a Kansas employer.''

Koch Industries, which has more than $25 billion in annual revenues, is the third-largest financial backer of Dole, the certain GOP nominee.

Federal Election Commission reports show Koch employees donated $16,500 to Dole's presidential campaign in 1995. Last July, David Koch, who with his brother Charles G. controls about 80 percent of Koch Industries, hosted a birthday party for Dole that raised another $15,000 for his White House bid. David Koch is a vice chairman of Dole's '96 campaign.

According to the magazine, the Select Senate Committee on Indian Affairs, after a yearlong investigation that began in 1989, accused Koch of ``the most dramatic example'' of a company stealing oil from tribal lands by deliberately under-measuring and under-reporting how much it took.

Citing sources familiar with the Senate probe, Business Week said Dole's aides put pressure on the committee staff to blunt the report, which Dole, speaking on the Senate floor, called a rush to judgment. Then-Sen. Dennis DeConcini, D-Ariz., Dole and others also challenged the reliability of testimony before the panel in two letters to the committee chairman.

Koch Industries denied the charges and a grand jury investigation, triggered by the report, was dropped in 1992.

In April 1995, the Justice Department filed a lawsuit accusing Koch Industries of more than 300 oil spills over a five-year period in six states, including Kansas, beginning in 1990. The matter is pending.

Dole was among several senators who sponsored the Comprehensive Regulatory Reform Act of 1995. Critics charge the act would help companies like Koch defend themselves against such lawsuits by citing conflicting federal regulations to prove that regulations had not been enforced uniformly.

Dole spokesman Hine said the protective provision was added by another senator _ Sen. Kay Bailey Hutchison, R-Texas, according to Senate staffers. ``Dole had nothing to do with it,'' Hine said.

``There's no story here,'' he added today.

Koch Industries Chief Legal Officer Donald L. Cordes denied the company ever perpetrated an oil theft scheme. And he said other companies, not Koch, lobbied for changes in the regulatory reform bill.