The paper describes the modified backstopping robust algorithm for time-invariant linear single input single output (SISO) plants with delay. It is shown that the proposed algorithm is realized by one filter on input signal with dimension n, where n is a plant order. The derivatives of stabilizing control signals are not calculated but estimated by using the first order observer. This fact simplifies analytical calculation of parameters of the control system and it technical realization. Algorithm provides tracking of a plant output to a reference signal with required accuracy. Simulations results illustrating an efficiency of proposed scheme are presented.