LONDON (AP) _ Multinational corporations should not be allowed to suppress criticism by filing libel suits, two vegetarian activists argued Tuesday as they sought to overturn a ruling that they libeled McDonald's.

``The point of serving libel writs is not to have a court case but ... to have a 'chilling effect' on free speech,'' defendant Dave Morris said.

Morris, 44, and Helen Steel, 33, defended themselves in the ``McLibel'' case, which at 314 days in court, spread over 2 1/2 years, was the longest trial in English history.

In June 1997, McDonald's won a judgment that it had been defamed by Morris and Steel, who had distributed pamphlets entitled ``What's wrong with McDonald's? Everything they don't want you to know.''

But it was a dubious victory. McDonald's is estimated to have spent $16 million on the case and did not bother trying to collect damages of $98,000 from the unemployed defendants.

The company also suffered the embarrassment of the trial judge's ruling that it was responsible for animal cruelty, that it exploited children through its advertising and that it paid its workers in Britain poorly.

The judge also ruled that substantial parts of Morris and Steel's leaflet were true.

In the start of their appeal Tuesday, Steel argued that a wealthy corporation can silence its critics simply by suing. The two had argued in the original case that their pamphlets were considered protected free speech.

McDonald's was due to outline its case later in the week. Its main attorney, Richard Rampton, estimated that arguments would take about two weeks.

The scene at the Royal Courts of Justice underlined the imbalance between the combatants. McDonald's was represented by two barristers in wigs and black gowns, while Steel and Morris _ once again arguing their own cases _ wore sweaters.